Can somebody explain this Islamic logic?

Okay, we always hear about the deal with the 72 virgins for those suicide bombers and terrorists who kill all those "infidels" but something doesn't make sense.....and no, it's not the obvious ridiculous aspiration of expecting eternal glory for performing brutal violent acts against other human beings....its the number ...72. Thats it, 72? You want me to be in paradise for eternity and all I get is 72 virgins? I'm here F-O-R-E-V-E-R and a day and all I get is 72 virgins? So lets see; if I "devirginize" one of these virgins once every month....I'd be out of fresh virgins in 6 years. You're in paradise for ETERNITY and you're out of your glorious prize in a short six years! Thats only one girl a month.....most guys will be done in the first week. And thats another thing.....what do the women get? The 72 virgin deal seems to be a little lopsided. While you ponder that, think of this......if the whole basis for the Islamic afterlife is rooted in a guys need to get off then how bad is "paradise" going to smell with all that you know what going on. Because seriously, you didn't expect that suicide bomber to blow himself to kingdom "come" to not be able to as soon as he got there; did you?