If the sales rep wants to be compensated for something beyond the first year then they must be actively involved in the upsell, crosssell, or the renewal.
Another thing to consider would be having the reps sell more than one year at a time. Multi-year deals can be beneficial for the org too such as attracting better logos, as well as improving cash-flow which can help offset the need for funding. I've seen multi-year deals truly be a game changer for Saas orgs.
My question for you would also be, where is your question coming from? Just curiosity? Do you have a sales rep complaining they should be getting comped? Are you working to build a customer success team and there seems to be tension between sales and CS?