That 5 date rule is sooo stupid!
Okay, it's not necessarily stupid to have the rule, but why tell the guy you're dating about it! 'Hey this is only date number one, but if you stick around till the fifth date you'll get laid for sure!'
Besides, it's weird to promise someone sex on a certain day in the future. What id you change your mind.
It would be better to say that you don't have sex on first dates, and that you want to get to know someone first.