Okay really how often does a man truely need to get off???

I'm getting super irritated... I try an keep up with my husbands sex drive as much as I can and apparently it's still not enough cause not even 2 days later he's masterbaiting in the shower....WHY.... and yea you can say well atleast he's not cheating but uhh picking his hand over his wife is kindof fucked...when he does it he doesn't even ask for sex that day or the day before.... ugh...rant over I suppose...