Talking dirty?

As often as it works for him and you don't mind doing it. I had a Girlfriend who wanted me to talk all the time. But personally I preferred now and then to have this unspoken passionate encounter. So I suspect that the balance is somewhere in between. Or you/he may find that the talk becomes more natural over time.

In my case all day long. But too much dirty talking can be frustrating for some guys as they may think there is nothing important in your life but sex.

If I were in your shoes, I would do it once a day and I would pay attention to my partner's reaction to deeply know his/hers personality.

Depends on the situation of the relationship.

If it's a standard relationship. I don't see the point.

If you see the person a lot, why not just be dirty instead of talking dirty?

From my experience, as often as possible. Guys are usually thinking about sex a lot more than we are and so any dirty talk is usually welcome.

Well if he likes it and it turns him on, whenever you plan to have sex or hankypanky.
Don't over do it and talk dirty to him all the time, it may make you seem sex obsessed.

It depends on what is acceptable to you and your boyfriend. It's all a matter of personal preference. I for one, like it a lot, but not every time I talk to him. If it gets to the point where you think that is all he is capable of talking about or all the he wants from you, then it's probably too much. Or if it gets to the point where you feel he isn't interested, then it's probably not enough.