I guess I interpreted OP's post wrong. He should get clearance. Trying to get 8 hours sleep on such an event is darned near impossible unless your initials are LH.
My average HR on a long brevet is often under 100 BPM and never above 120. My Cardiologists told me they would be more worried about orthopedic issues than cardiac doing such a long rides. Nonetheless, I do agree too many long distance events can be counterproductive. Interestingly, Mark T. had a coach helping him prepare for a Charly Miller ride and she cut his mileage and brevet schedule rather significantly. So, you have a good point Steamer.