i dont think you can set a time limit for sex, in my oppinion just whenever you are ready is fine, and that could be different for different people you are with.
i had sex with my boyfriend (well now ex) about 2 weeks after we started going out and i was a virgin, and i had been thinking 'im not ready yet' but it was only because i had this idea in my head that you should wait a few months first. but i actually really wanted to sleep with him so i did. i just felt very comfortable with him.