My husband has done two fleches, a bundle of 400s and 600s, 1000s, and 1200s (and I'm stinkin' proud of him because he did PBP last year and had so much fun!). He always brings a change of shorts if the ride is 400 or longer. He probably brings two on the 1000+ rides.
The randos around here swear by Lantaseptic.
"My predominant feeling is one of gratitude. I have loved and been loved;I have been given much and I have given something in return...Above all, I have been a sentient being, a thinking animal, on this beautiful planet, and that in itself has been an enormous privilege and an adventure." O. Sacks