WMK,

That's the approach I went with for the PFP recurring.
1. Setup avail "schedules" on the admin screen.
2. Link certain "schedules" to certain "products/models" through the admin screen.

User Experience
1. Add a product to your shopping cart.
2. Add checkout there is another box/pane that has listed the items in your cart that can be "renewed". The user checks the items they want renewed, and the number of terms they want renewed.

At checkout, the item is purchased as a regular sale item, and a recurring profile (on the PFP side) is setup for the remaining n-1 payments.

I like this loose coupling of recurring items. A user is really just saying "Hey, could you just purchase this same item X times at Y intervals?".
This them also seperates the logic of what happends when a certain "item" is purchased.