The current implementation of subscriptions in the dotnetnuke core allows the processor to do the recurring processing with a notification to the site to extend the period of access. You can still cancel the recurring nature and enjoy access for the period of payment.

I have noticed a number of sites (such as clipart.com) uses a slightly different tact, they just use the processor to just process payments and when someone logs in from an expired account they have the option to extend.

Which method do you prefer?