We pose the question: is it possible to get a future proofed machine, that will last me the next 10 years?
There are three aspects to this, hardware, software, and warranty.
As you are probably painfully aware software changes every 5 minutes.
PC's are designed to be able to keep up with all but the largest possible changes. A large change like upgrading to a new version of Windows may bring bugs and performance issues with it, so if Windows updates it is probably time to buy a new machine, or be prepared to work through it. However I will say this, my Windows 7 PC handles Windows 10 delightfully, but it is a self-built beast and has had an SSD upgrade.
Microsoft will stop supporting old versions of Windows 10 roughly 18 months after they are released. As long as you apply all major updates offered by Microsoft, Windows 10 will be your "final" version of Windows, evolving to each next version with an easy upgrade path.
Whilst there is always the latest model, latest resolution and power, hardware changes relatively slowly compared to software. That said, hardware does wear out. SSDs (the heart of the PC) have a lesser lifespan (at the time of writing) than traditional HDDs, but the price has come down so they are affordable to replace*. Typically with hardware the higher the price the better lifespan you are buying into; this isn't true with very highly specced components though (e.g. an overclocked CPU) as they are running at the edge of their tolerances and will wear out faster. Spend more to get better quality, speed, and lifespan.
*replacing parts yourself will invalidate the warranty.
Additionally, “higher-end” machines are usually easier to upgrade. Often, remove 2 screws, remove the old part, fit the new one, and replace the screws. On more budget machines, parts replacement can be more complex – involving stripping the machine down to component level, and rebuilding it. This is typically work only an experienced professional can carry out, increasing cost.
The kind of warranty we recommend is, for example, Dells next day on site 3 - 5 year warranty. Any hardware issues get fixed the next day, which keeps your business going with minimum fuss. Once a computer is out of warranty, it could cost as much to fix as it is still worth, at which point it's time to buy a new one anyway. We think that the lower specced machines (like Dell Vostros) are okay to last 3 years with that length warranty, and that mid-range upwards (like Dell Lattitude and above) are okay for 5 years.
Remember than any upgrade you do will probably invalidate that warranty unless done by a registered [Dell] engineer.
You could spend a lot of money on a very highly specced machine but it isn't going to last forever, and 10 years is a stretch. For 3 years troublefree computing almost any model will do, like the workforce favourite Dell Vostro models. For 5 years, spend a little more and get a bit more life out of it, or at least something that is easy to upgrade (invalidates warranty) like a Dell Lattitude, or Optiplex. For 10 years, stick your head between your legs, and hold on.