I was taught by my instructor 3 flight is good, 4 is ok, after that be careful. Now this guy has been in the hobby long enough that I think he taught Orville and Wilbur to fly RC.
Since that time I haven't found anything to change that suggestion. Windy days or when i practice touch and go's i'll fly 3 calm days when I'm being lazy I'll do 4, then I'll check the batterys
Good Luck Have fun