You don’t think an M1 will last for say 10 years? I’m close to 11 on my Win machine.
M1 can easily last 10+ years. But Apple will "vintage" the software over about 7 years and M1 has been around a few years already. Once you get 2 generations beyond an Apple hardware generation, various new features start "no longer being possible" (unless third party hacks are applied) on older technology. And once macOS updates end, many Apple apps will "upgrade" out of compatibility with the older Mac. For example, the iWork apps are notorious for this.
On the other hand, Windows tends to not be in such a hurry to leave old hardware behind. Some might even argue that Windows supports older hardware for too long. Those with old Intel Macs entering or beyond vintaging can give them second life as a Windows PC because Windows will likely support them quite well.
Apple wants all to buy new hardware as soon as reasonably possible. Hackers will show that old hardware can run new macOS just fine, but then you are leaning on hacks that can break with each software update. If hackers can make new macOS run on older hardware, Apple can obviously do it too. So why don't they? The current way makes lots of money. This other option makes no money.
So, yes, you can save some money by buying M1 Macs after M3 release. However, you "pay" for the savings SOONER because that "new" (to you) Mac will be vintaged much sooner than buying "latest & greatest." Once vintaged, key apps will stop working in full (Safari for example will increasingly not work as a browser) and other apps will not be compatible with the same apps updated in newer version of macOS: for example, friend sends you a Keynote file created in newer macOS version and it probably won't open on the latest version that you can still run on your vintaged Mac.