Unnecessary to float them or anything like that. Once you get used to using canisters, it only takes a short while, all you have to do is to shake them and you pretty much know how much is left. Or you also know just from the time you have used them. A small one last me 6-7 days (in a jetboil, doing 2-3, 2-3 cup heats every day), a larger one, twice that. when I shake them and I feel nothing sloshing inside, that means I have only a couple heats left.

It's really simple.