The only restriction I'm aware of is when you're on Reserve. The system will only allow you to pick up a little bit of flying in between your Reserve blocks inorder to assure that you're legal to fly if called. I suppose you could drop your entire month if you were able to find another pilot to fly the trips. Some FA's are notorious for doing this. They'll work a couple trips A YEAR in order to retain health benefits and maintain the minimum currency. They're usually the senior mamas who can give away everything.