Not to a be a noodge, but getting 15 years of service from a computer is literal, actual insanity!
A
pan wouldn't be expected to last that long, nor a sofa, nor a car! And they are not bleeding edge, luxury items!
FWIW, the rate of advancement in computing has been slowing for some time, now. CPUs have made no leaps in 7 years, only incremental upgrades. The last 20 years contained some scary big changes because a lot of what was set out 5 decades ago when computing began was ill conceived. It has all very much settled down, now.
However, those who choose to buy the cheapest item they can at the point of changing their setup will still be in a for a bad time. I understand constraints in money - better than most, believe me - but you cannot have it all the ways. If money is your defining limitation (as is so often that case) then you have to accept what you can get for what it is. At that point, gaining a deeper understanding of your device's working is highly recommended. After all, if you must have a car for work, but all you can afford is a junker, you had best learnt to service your own engine.
This is the other area in which Apple products break the usual curve. A Windows laptop bought today that is anything less than flagship has halved in value by the time you get it out of the box. In one year, you wont get 20% of its cost back at the point of resale and in two, it is more or less worthless.
A MacBook bought today can (crazily enough) increase in price for the first 6 - 8 months, and will then hold onto at least 80% of its value for the first two years. Even ten years hence, the Mac will still have a solid chunk of its value left, and not because of collectors, but because the thing will still
work! After ten years, all a windows laptop can hope to do is prop open doors.