Don't ride continuously for more than 2 hours then! You are allowed to stop whilst out on a ride, have a drink of water, get off and walk around, have a look at an interesting building etc.
I never get on a bike and ride it non-stop for three or four hours. I might be out that long for a ride if I'm in the mood, but I'm not moving all the time. if I spot something I'm curious about, I get off and have a look. When I want a drink I get off. If I've taken any food with me (very rare) I stop and get off to eat it. The few minutes you spend off the saddle here and there over the course of a ride is what prevents the numbness and discomfort from building up. It also prevents stiff necks and numb hands.
I never use saddle covers, padded shorts, or any other sort of cycling clothing. Sometimes I will even ride in denim jeans - although not in really hot weather.