Butt pain is my problem. I can ride 30 miles with only mild discomfort, 40 miles is painful and 50 miles finishes me.
I do not have the budget to try numerous $75 - $150 saddles until I find one that works for me. If such a beast even exists.
I would love to ride a century, I don't think my legs or stamina would be a problem but the butt is my Achilles heel.