If you want to allow a customer's subscription to renew one more time and then automatically expire at the end of that billing period:
1) Go to the Subscription box and click Options.
2) Select Edit Subscription.
3) Scroll down to Timing and go to the REMAINING SUBSCRIPTION TERM field.
4) Enter "1" into the field.
5) Select "Expire subscription" under AT END OF SUBSCRIPTION TERM.
6) Save Changes.
This action will update the subscription so that it allows for one more renewal. At the end of that billing period, the subscription will then automatically expire.