Castelli Endurance X2 Bibshort
Castelli made the Endurance X2 to handle your longest rides. They upgrade it with color-matched Giro++ grippers and the new Progetto X2 pad. Action fabric with ProSecco treatment throughout the short means that it's not only extremely comfortable but also extremely durable. This one's made to go the distance.
Just got these, so no opinion yet on whether I like them (ignore the Stars on this review). Sizing is tricky. I'm just under 6 feet and about 170 lbs. I've always worn size M bibs (I've owned Pearl Izumi, Assos, Nalini, Santini and REI brand over the years). I read lots of comments that Castelli runs small so I ordered these in Large and I'm glad I did. The fit on the shorts feels great, definitely not big or baggy. BUT, I'm just under 6 feet tall and just trying these on the shoulder straps are clearly going to be uncomfortably short (and they are narrow). I'll keep the shorts and hope the straps stretch with use.