Here's how to reuse an open can of Great Stuff.
When you're finished with your project, put a long pipe cleaner in the tube and tooth picks in the can nozzle and dispensing lever. Wait overnight until cured or until your next project and pull the things out. You'll be good to go. Great Stuff used to publish this information in little pamphlets on their cans, that's how I learned of this. I'm sure they figured out that it is more profitable to withhold this information. A dispicable approach to business in my opinion.