After a successful session in the sack, you might be ready to call it a night—but what if she’s looking for an encore?

Unlike women, guys must take into account their refractory period before they can consider having sex again. This refers to the time lapse between your initial orgasm and when you’re able to experience an additional ejaculation and orgasm.

And unlike what you see in movies, the notion that you should be able to have sex three or four times within a few hours on a Saturday night probably isn’t realistic for most men, says urologist Richard K. Lee, M.D., of Weill Cornell Medicine.

“Unless you’re 14, you’re probably going to need at least an hour or two to become erect after ejaculating,” says Dr. Lee.

In fact, there’s no hard data on how long your refractory period can last. However, estimates range from 30 minutes to 24 hours, and it likely increases with age, according to a new review in the Journal of Sexual Medicine.

Scientists aren’t exactly sure what’s responsible for the latency period. But research suggests that post-orgasmic spikes in the hormone prolactin—which hinders arousal and ejaculation—may contribute.

Certain lifestyle factors might also play a role. Drinking alcohol or masturbating regularly could further extend the time it takes you to recharge, says Dr. Lee.

But if it seems to take you days to regain your ability to function sexually, tell your doctor, Dr. Lee advises.

He or she can help figure out if lifestyle habits are hindering you from getting hard, or if other factors—such as stress, new medications, or health conditions like heart disease—are causing actual erectile dysfunction.