Iver,
The initial type freeze is 5 years. You can bid for a new type every year if you wish, it only means that the company don't need to honor your bid if you are frozen. If, however, they desperately need you they will waive the type freeze and give you a transfer if you bid for it.
Be aware though that you might bid for something in a previous bid that then gets pulled up for transfer. The golden rule in BA is only, only, only ever bid for what you want. Never bid for something on a whim that you subsequently don't want to do.