Hi Mizzo79,
The physical answer is that 30 minutes should do it. But honestly, I've gotten away with launching 5 to 10 mins after coming back in the past.
Psychologically, the answer is very personal. Integration time is important. But listening to the call is also important. Balance is desirable. I don't think there's anything wrong with heavy use is one is getting a strong call and managing one's life. This means meeting all expectations and obligations, work, school, personal, etc.
In the past (2009-2010) I used DMT a lot, sometimes multiple breakthroughs in a day.
I took a long break after 2017 and came back to it a couple years ago and was doing it every 2-6 weeks.
I'm on another long break and if I ever get back to it I suspect my use will be very infrequent.