How long do you know a guy/girl before sleeping with him?

My friends have some funny rules that they would jump into bed with guys that aren't their 'potential husband' materials but pretend to be a ''good girl'' when they've found some decent guys.

I have similar rules:

I would jump into bed with girls who are not "good wife" material; and remain platonic friends with good girls who want to marry me:-)

i think as long as u keeping to your rules, it is ok

It is very important to be consistent in keeping one's rules in any relationship. If girls have no intention to sleep with me, I will dump them after maximum 2 months dating. Otherwise it's wasting my time and money.