How long are the contracts? Well you can upgrade at any point and they're fully flexible after the first 6 months, so as long as you like - but you do get the option to buy the bike after a length of time.
We think you will want to upgrade before you reach these points as your child grows. But it's only fair to offer you the bike if you do want to hold onto it. We like being fair to customers, it makes for a happier Bike Club.
You can still buy the bike and upgrade, whatever is easiest for you. Oh, and like a phone contract we offer you an incentive to upgrade.
We try to be the most affordable way to get children out riding great bikes. Hopefully this helps.