For me, it is very simple. I have a low tolerance. I can't take more than one or two tokes without getting uncomfortably zonked. Getting truly "wasted" is no fun. For me, if I toke too much it usually results in anxiety and paranoia, which is worse that if I hadn't toked at all.
But as you said, if you stop after one or two tokes, most of what's left in the bowl will continue to burn and be lost. With most vapes, that is. So I'm looking for a qualify on-demand portable. That stops burning after you stop drawing. Not really interested in a desktop.
Good bud is a terrible thing to waste.