Especially if it's been a really, really long time or if it just happened. Talking about a long dry spell is sad and will make your date wonder if you are perhaps bad at sex. Talking about sex you've had recently is more information than is called for. Talking about the sex you've had with other people is irrelevant to the date you are on, assuming that part of your dating goal is to find a new person who might, in the future, have sex with you.