A former employer required a bond for recurrent, which limited you to timing your departure for another opportunity. Finally, I just bit the bullet and left. Pilot recurrent training is part of doing business and if its cost will make or break the operation, then they probably shouldn't be in the airplane to start with. Another employer required a contract for an initial type but after 24 months, the contract was fulfilled and you could leave free and clear. If you spend any decent amount of time with a single employer, my view is that they've gotten their moneys worth out of you and shouldn't require anything from you.