Well do we really always want to use the absolutely thinnest condoms. What if the girl's amazingly hot! Then instead of lasting 15 minutes, you blow your wad in 12!
Isn't the point of screwing to last as long as you can and then explode just before the agents calls. I think every guy should carry a selection of condoms all nicely laid out according to thickness. Then after sizing the girl up, you pull out the Okamoto, Durex, or whatever.