It depends on your usage, but it can take less time to be inconvenienced because your computer doesn’t support 1) handoff, or 2) won’t unlock with your watch, or 3) doesn’t support sidecar, or won’t update the reminders on your iPhone, or 4) launch the Home app so you can see who is at the front door, etc…
Most things are novelties, nothing really earth shattering for professional usage.
1) I used "handoff" from 2010 till 2022 without using Handoff...it's called using the iCloud with doing an extra manual step, namely saving your changes explicitely in the iCloud. Most professionals will still do that step because you really do not want to take any chance on losing your last updates by trusting any piece of software.
Don't believe me? Well every professional will click on the "save"-icon in Ms Office before they close the application although any Office application automatically saves at the moment of closure from the early 2000's onwards.
2) Unlocking your professional Mac by another electronical device is frowned up, you unlock a professional used Mac manually by adding a code in or using your fingerprint, never by an extra electronical device that sends out a signal.
Don't believe me: take a look at most car leasing companies that don't have keyless entry in their option list or if they do, the insurance goes up with a decent amount
3) Sidecar...really? Maybe for a consumer or a prosumer when they are working in a hotelroom, but most prosumers and all professionals will invest into an external screen once it becomes clear that this is needed.
4) The working of those types of apps is linked to the version of the operating system of your Mac and to the hardware for which they are created, not really the hardware of your Mac. Logically the app will stop working because it doesn't support anymore the newer version of MacOS (ergo younger software) you have installed that is still supported by your Mac, not the other way around.
There is something to be said for a stable platform for 100% work, but it‘s impossible for you to future proof a computer because you have no idea what’s coming in the future.
It's not impossible at all once the hardware (GPU and CPU) architecture is known.
The M2 will support the functionalities of the M1, just as the M3 will support the M2 and M1, etc... If Apple wouldn't do that it would mean that their hardware in one eco system would stop supporting any software created for that eco-system with every natural hardware evolution.
That would be a very bad business idea.
Your MS Office 2021 for Mac bought for a Mac M1 will still work in 2030 on the Mac M10.
This is the birth of Apple Silicon for the Mac, and the pace of change will be much faster than it was when you bought an i7. Maybe that’s why Apple didn’t release an iMac Pro. A high-end all-in-one could quickly become outdated with the next M series chips. At least this way we can trade in the Mac Studio in a couple of years but keep the monitor.
The pace will be at top speed a new M-version a year, each M-version will support the "legacy" architecture of the previous systems within the same eco-system. In this case it's the Silicon eco-system, justlike we had the Intel eco-system and before that the PowerPc eco-system.
The only thing that can really break Future proving is when Apple has an hardware Revolution instead of Evolution, namely when they switch architecture (PowerPc to Intel to Silicon), but if you are one of the people that bought a powerful Mac at the end of a such a cycle, you will have a minimum of 3 years where the old and new eco-system are supported, followed by another 3 years where your software, except your OS, will support your professional work without any problem at all.