I have to disagree on this, I don't think it will matter in the slightest. Apple has probably decided how long they are going to support Apple Silicon for a while already and specs don't matter. 8GB, 16GB or 24GB won't matter.
What matters is the OS of launch and sometimes the product category (for instance with iPads, the air, pro and mini have the same support, but the base iPad has 2 years less). We could have for instance 7 OS updates for the regular M Macs, 8 OS updates for M pro and max and 5 or 6 OS updates for the A series.
We will know once each products stops receiving OS updates (security updates past the last OS updates are a different story, they are generally only for the most important security issues, so not full, and generally continue for a couple of years after end of software support).