There certainly are 10 year old MacBooks out there, in active use today, but... a) not many, and b) I don't think the people using them are having a very good experience.
This bears mention. I buy Macs because they're pleasant to use, fast to get what i want done, etc.
If you're trying to push ANY machine out to 10 years, after 5-6 its going to be a basket-case, i don't care what spec you buy. Your CPU/GPU won't have support for newer video codecs, your storage will be slow, your RAM capacity will be tiny by the standards of the day at that point. The user experience will be trash.
Replace after 3-5 years. If you can't afford to do that with the Apple hardware you think you want (trying to think you can push it beyond 3-5 years), do it with lower spec apple hardware, or cheaper PC hardware. On balance you'll get a better user experience than trying to push hardware way beyond its design life.
People running most if not all 10 year old macs (or PCs) today won't be able to play HD video, especially not using h.265 (less bandwidth). They'll be on crappy old 802.11G wifi, a spinning hard disk, slow USB2 ports and most likely have 2 GB of RAM (or less). The battery (if a macbook) will be dead, and even if it was new, the battery life will be 1/3-1/2 of a currrent machine. To put it bluntly, the user experience will be crap. And you don't buy Apple hardware to have a bad user experience.
edit:
When i say "replace after 3-5 years", what I mean is this:
- bank on the machine being good to use (and under applecare, so if it breaks, free replacement) for 3 years. after 3 years your applecare runs out and IF it dies you need to have the money to replace it. so be saving for it and ready to buy after 3 years.
- in reality, if the machine doesn't die after 3 years (most don't) then it will still most likely be "fast enough" and have hardware support for most of the stuff you want to do for 4-5 years. keep saving your money through year 4 and 5 for a nicer machine to replace it with, or use the extra money you saved for something else.
- by year 6, your machine is 2 full life-cycles old. it will be long in the tooth and quite slow, doesn't support current standards, etc.
Computing hardware is generally designed with 3 year life cycles in mind (tax laws in various countries allow you to "write off" 3 year old machines for tax purposes - and this is why extended warranty is 3 years). SOFTWARE is generally designed with "current" generation (i.e., within last 3 years) and possibly 'previous' generation (3-5 years) hardware in mind.
After 6 years your hardware spec is not going to be targeted by most developers (this is why MS drops support for Windows after 7 years, and why Apple also drop support for older macs at this sort of age). So they will be assuming that machines have more ram, updated CPU instructions, etc. than your machine has - and using those resources to do more things.
AS others have mentioned above if you're willing to just run old software you can maybe stretch it, but again... security issues, lack of compatibility with other users, new internet sites, etc.... just gets painful.