I have a Lenovo ThinkPad T510 purchased about six years ago. I’m perfectly happy with it, except the keyboard needs replacing and batteries seem to lose their ability to charge within a couple of years. The keyboard and battery could be replaced for less than $100. Other than those factors, is there any reason to replace the machine? If I buy a Windows 10 machine, could I or should I continue to run Windows 7 on it? Pablo

There is no universal answer to your first question. The time to sell, repurpose or recycle an old PC depends on a large number of factors. Some are technical, such as the specification, the build quality, and whether it will actually run Windows 10. Some are personal, such as what you use it for, how much money you can spare, and whether your time has any value.

Circumstances alter cases. It might not be worth replacing a very old PC that’s only used for personal emails, especially if the user is short of cash. On the other hand, it could make sense for a company to replace a high-spec machine that is only a few months old if time is extremely valuable, as it can be in financial organisations.

However, your second question is easy. Windows 7 was launched in 2009, and reaches the end of its supported life in January 2020. After that, there will be no more security patches except for the companies able and willing to pay. I understand that Windows 7 Extended Security Updates for Windows Enterprise Edition will cost $25 per device for the first year, $50 for the second year and $100 for the third year. Windows 7 Pro charges are twice that, but still only half the typical charges for extending Windows XP support.

Given that Windows 10 Pro can be set up to look and work much like Windows 7 Pro, it makes no sense to pay to extend Windows 7’s life unless your business absolutely depends on it.

Even if you disregard the security risk, it’s a bad idea to try to run Windows 7 on hardware designed for Windows 10. Manufacturers don’t test their machines with obsolete operating systems. Even parts on the QVL (Qualified Vendor List) are not guaranteed to work.

I am not saying it can’t be done. I am saying you should avoid it as an unnecessary risk.

Six and out

I replaced my previous laptop and desktop PCs when they were six years old, and I think this is a sensible strategy. Old machines may still work, but usually they will have been left behind by technological advances. In your case, the T510 is missing the UEFI system that provides fast start-up, M.2 slots for faster SSD modules, USB-C or Thunderbolt for faster connections, better on-chip graphics with video support, a camera for Windows Hello face-recognition log-on, and so on. You’re also missing out on a touch screen with tablet and pen capabilities.

Of course, you can improve the performance of your Lenovo ThinkPad T510 by adding more memory and swapping the original hard drive for a fast SSD. Not everybody can. We’ve all seen the trend towards sealed cases, soldered-in memory and storage chips, glued-in batteries and so on. These make laptops more expensive to repair or upgrade, and therefore more disposable.

Old PCs also consume more power, which makes them more expensive to run. Mid-range processors have not become dramatically faster, though having (usually) more cores does mean they work more smoothly. For the past decade, Intel has focused on providing more performance per Watt, rather than more raw performance. A typical laptop processor now runs at a TDP of about 15W, going down to 6W, instead of 35W or 45W. These new processors generate less heat, so they can be used in thinner, lighter and more portable laptops. Lower power consumption also provides longer battery life.

Incidentally, I don’t feel bad about retiring laptops after six years, partly because I used to retire them after three years. My laptops do a lot of useful work and generally cost about the same as or less than smartphones that do less useful work and only last half as long.

Also, I value my time, especially as I get closer to my own end-of-life recycling point. Some people think they are saving resources by using old machines that can’t cope with dozens (or hundreds) of browser tabs, take ages to download bloated web pages, are slow to load programs or copy files or whatever. That’s a waste of human resources. I won’t waste mine.

ThinkPad T510 pros and cons

The 15.6in ThinkPad T510 was a premium product designed for corporate use, and far better made than the average laptop was back then, or is today. It appeared around the end of 2010, so the design is nine years old. Its premium features included a Firewire 400 port, which you probably don’t use. The main problem is that it’s not on Lenovo’s Windows 10-compatible list. However, some people have managed to install the 1903 version, so you could download it and have a go. If it installs, your Windows 7 product code should authenticate it, so you won’t have to pay for it. And if all else fails, you could install Linux.

Sadly, even if your ThinkPad T510 runs Windows 10, it has a lot of limitations. These include the screen resolution (1366 x 768 pixels), slow USB 2 ports, the fairly slow drive speed (SATA 2 is 3Gbps not 6Gbps; no M.2 slot), the lack of memory (8GB is the max), and the slow CPU.

The T510 is, as mentioned, upgradeable. You have 6GB of memory so it’s probably not worth replacing a 2GB simm with a 4GB module to raise that to 8GB. However, it would be worth swapping the hard drive for a 250GB or 500GB SSD, costing $49.99 or $66.99 at Crucial’s US site. You may be able to find cheaper alternatives where you live in Mexico. An SSD would make a significant difference to your laptop’s responsiveness.

Unfortunately, you cannot do anything about the first generation Core i5-540M, though it has held up pretty well. The i5-540M has a Passmark score of 2,452, which is the bare minimum for running Windows 10 at a usable speed. Basically, it’s as fast as today’s Intel Pentium Silver N5000, which is a cheap, battery-efficient 6W chip. The Core i5-540M has a TDP of 35W.

If you were to buy something like the T510 today, you’d probably get a 15W Core i5-8265U or better. I regard the i5-8265U as the starting point for serious laptops, and it has a Passmark score of 8,000. It has four cores and eight threads, where your i5-540M has two cores and four threads. According to the UserBenchmark website, the i5-8265U is 141% faster, and if you’re using all the threads, it’s three times as fast. You would notice the difference.

Options?

If you don’t want to spend a lot of money, put what you would have spent on your T510 towards a refurbished ThinkPad with a much more recent processor, such as the T440 or the X250.

If you want to replace your T510 with today’s equivalent, I’d go for the 14in T490s rather than the 15.6in T590. That would get you a Core i5 or i7 processor, 8GB or 16GB of memory, a choice of SSDs from 128GB to 1TB, a good Full HD (1920 x 1080-pixel) screen and a great selection of ports including USB-C/Thunderbolt 3. It’s 16.7mm thin and weighs 1.35kg, where your T510 is more than twice as thick (35.8mm) and more than twice as heavy (2.8kg).

There are, obviously, much sexier options, such as the ThinkPad X1 Carbon, and the Yoga C940 with its 10th-generation Core processor.

But anyone spending that sort of money could put off purchasing a new laptop for about a year or so, because dual-screen machines look like the coming thing. The Asus ZenBook Pro Duo UX581 is a stunning piece of work, while the 14in ZenBook Duo UX481 is a more portable, and more affordable, alternative. Last week, Microsoft previewed its own dual screen machines, the Surface Neo Windows laptop and the Surface Duo Android phone, due about a year from now.

Microsoft and Asus have been messing around with “auxiliary displays” since at least 2005. Asus showed a prototype hinged, dual-screen ebook reader in 2009, and the Microsoft Courier attracted some attention before it was cancelled in 2010. More recently, Lenovo had a go with the Lenovo Book, which transitioned from Windows to Android.

I’ve seen a lot of terrible machines, but the Surface Duo looks like the real deal. I expect all the leading manufacturers to launch their own versions, which will establish it as a new form factor, as happened with the Surface Pro. I wouldn’t be shocked to see a dual-screen iPad…

Have you got a question? Email it to Ask.Jack@theguardian.com

• This article was amended on 10 October to correct the description of the Surface Neo and Surface Duo