We are always reluctant to go past 3NT in the bidding, particularly when rebidding a minor suit after partner bids of 3NT. Here is a hand I held as South recently where I faced that dilemma:
My hand values at 20 points after partner rebids her clubs (the club queen will fill in her suit). I jump to three diamonds at my second turn, forcing to game and showing slam interest. Do you agree with my action so far? What would you do after partner bids 3NT?
I chose to pass. That was a mistake in retrospect. By rebidding four diamonds, we can reach a minor suit slam in diamonds or clubs. My hand to too unbalanced to sit for 3NT.