Using Pricing Rules to Extend Membership Expiration Dates

Hello!

At Georgia Aquarium, we sell memberships as ticket products.  We are getting ready to sell a 14-month membership.  At TLCC, I heard mention of using pricing rules to extend membership expiration dates.  We are currently using source codes and then running a utility on the back end to do it but that doesn't work as well as it should for us.  Does anyone have information on how that is done?

Thank you!