I would give my opinion from a male's stand point. As long as you like it, and you still can have it, there is never too much. For me, the most orgasm I ever had in masturbation in a day is 11. Although at the end, the intensity is a lot less , still I still feel the sensation.
Usually we can achieve more in maturbation than sex because there is less work to do lol plus all you have to care about is yourself. While having intercourse, you have to care about your partners too.
Usually achieving 3-4 times of orgasm in sex or masturbation isn't that difficult. It is usually more of "not having time" than the lost of interest.