That’s the theory, and it works like that on my MBP. But for some reason on my old iMac, snapshots used to just accumulate and every so often things start crash

That’s the theory, and it works like that on my MBP. But for some reason on my old iMac, snapshots used to just accumulate and every so often things start crashing because there was no space left, causing all sorts of issues. Sometimes the OS couldn’t boot because of that, it really was a pain. And yes, you can nuke snapshots preemptively, but often the first visible sign was Mail having corruption issues because it’s database was borked, at which point it was too late.