I understand the trick is to break the microbeads of glue on the back of them so they stick to the model, but of course there's no way of knowing exactly when that happens during the burnishing process.
Yes, I'm not even sure what that means... Sounds like one of those explanations designed to fob off those with supposedly less technical knowledge
Having applied one decal slightly wonky I was able to peel it off easily, in one piece, with masking tape. Basically that, the post it note, and the above method with the size, all seem to show that they'll stick to whatever is the stickiest.
I suspect it is true that the over time the wax they are printed with becomes less tacky due to drying out, dirt, oil, etc. so that you need more tack on the surface you want them to stick to.