If I used MissionMinder for our upcoming mission trip, but then cancelled because we wouldn't need the service for several months afterwards, what would happen to the data? Am I able to re-activate the account at a later date or would I need to start from scratch again?
You can export all your team and donor data to spreadsheets and save a lot of your stuff that way. Then perhaps save your other pages as PDFs. But yes, - for the most part you would be starting from scratch.
So far, most of users keep their account active year-round, so they can go back and reference / copy from old trips.