When my butt starts hurting on a ride depends on a lot. Cadence is one of them. Intensity is another. Time on the saddle yet another. Anything under 40 miles or 4 hours seems to be fine. Once I get over that time/distance, I start to have to add in creams and salves to make it all work.
I try to get off the saddle for a couple of minutes every hour or two. If I'm doing a long, multi-day ride, then I apply chamois cream every 30 miles and use Desitin as soon as I get off the bike, preferably after a shower.
I'd love to get to a point like others here that are riding 120 miles without cycling shorts and no issues. I have a hard time imagining that happening. Then again, I'm 280 lbs. I'm putting down more pressure on the saddle than most.