The average number of wet dreams (nocturnal emissions) among males older than 20 is once per month. Men at 40, emit sperm during sleep once per 6 weeks on average. When you are 50, you can expect to have a wet dream once every 2 months.
If you have wet dreams more than the average, it's still O.K. it means you're excessively horny and preoccupied with sex more than the normal man. Be happy with that. It's a good thing.