My experience has been that the hybrid systems don't need anything, basically ever. The hybrid system in my Insight has been chugging along for 16 years without a hitch, ditto with my wife's Civic Hybrid.
You might find this site useful:
Long-Term Quality Index
Over the ~20 years this site has been collecting data, the only manufacturer that's
less reliable than Volkswagen/Audi is Mini (and Smart, but I don't think they count for anything):
It's worth noting that Honda's score was pulled down mostly by Suzuki's they've sold on their lots branded as Hondas, and by the transmission issues for Accords in the early 2000's.
Across the board, Toyota leads the charts, with the Prius being the most reliable compact sold in America:
