IIRC (as it's been a few weeks since I've been working on it), will be handled in two ways. Either you setup recurring billing with the payment service provider, or it will be a manual billing (as you have described). I don't see why the user would make chargebacks, if there is a sufficient description attached to the bill. Expired credit cards will result in account suspension, giving the user the ability to renew their account.

You should really check out Gossamer Forum 1.2.0 if you want to see how the payment system will be implemented as it will be done in a similar manner (minus things like accounts by donation).

Adrian