Dover - LOL :^O

Beebop - now you're makin' me nervous - I've got 2 cans worth planted, but you're sayin' they might not make it?
I just wanted to control them, not kill them

And...what more than one of you have said about cats rolling in, and chowing down on the stuff was why I originally asked - mint or nip. Because I have (ahem) several cats and altho they do play in the stuff, they don't play in it anymore than the feverfew, or other places in the yard where they can 'whiz' :^O by you.

And...(don't I ever shut up?) if the choc. mint and the catnip cross pollinate, will I end up with chocolate nip? :^O If so, then I may roll in the stuff myself :^O :^O :^O Kitt

Well,
the great thing about using sheetrock-mud buckets is you can leave the mints for just about ever. When they eventually spread to the interior sides it's easy enough to spade a plant section out and throw some soil back in the space that's left in the bucket. And they always have more than enough depth.
Healthy mints develop really good root systems and some depth and breadth is preferable.
I didn't mean to worry you - the coffee cans wouldn't be my choice but that's just me. I'm admittedly influenced by many, many years of growing and gardening for people who were paying me a lot of money to get their estates right. So I lean toward methods which may be more work initially but save work in the long run, and which avoid plant failure. I couldn't afford plant failure ever. It's just a different world from doing one's own garden, there's pressure.
Your mints may do fine - I was just saying that if they don't, you'll know why (root-crowding and/or girdling) and will be able to correct the problem. Work a little bit of sand in, too, they like a bit of sandy feet. 1 part sand to 10 soil/compost works well in my area of the world for mints.