62 days is the longest you can rent a vehicle on one Hertz rental contract. I've done it in the last year (LAX). More than that and you get a Hertz lease Monthly Car Rental | Hertz
Terms under the lease are different than a rental 62 days or less.

I've purchased, and am still under a year long policy, InsureMyRentalCar.com insurance but unfortunately they are no longer writing new policies. 31 days is their maximum (was 62 days previously) but there is no verbiage about back to back rentals. It was pretty cheap ($172 for a full year - expires next March for me). You might want to search for a similar type policy.

No credit card insurance is going to be valid on a three month lease.