I have found that with POR you need to follow their directions to a tee. also that stuff goes a long way and does not store well once open. so smaller cans are better. I often by 4oz cans. i'd never buy bigger than a quart.

Yup. I buy the six packs more than anything else.

If you put a piece of plastic, like from a plastic grocery bag, between the lid and open can before you close it the seal is substantially better. I've had opened cans hold for a year or more this way.