Everybody's Mileage Varies, Butt... boy do I love my Assos creme for long rides (over 50 miles). Certainly, clean shorts every day, hygiene is a pre-requisite but not sufficient...
I don't want to be coarse, but when I used to go on multi-100-mile day trips, the part of me covered by my chamois was bruised and blistered. I resisted trying the Assos creme because.. well, because it's butt cream. But once I tried it and completed that two day trip with Assos, I'll never do long rides without it.