When to sleep with someone is a great question. I don’t believe there is any set time limit.
Men do tend to value women more when they take the time to get to know them little by little, though. My best advice to you is taken from Evan Marc Katz: “Your sole responsibility before having sex is to figure out if he’s interested in YOU or in SEX.
If you don’t know the answer, don’t have sex. If you think you know the answer, then have sex. And if you can’t handle the emotional consequences of making an occasional mistake, you probably shouldn’t sleep with anyone until you’re in a committed relationship.” And remember, you can’t go wrong with the right guy. – Tango