Rarely is a question asked on this forum without personal experience attached, so here's my reason for asking...
My son (2016 LHP) recently threw a bullpen for a "guest" pitching coach at his HS. This coach is highly respected in our area and has a son who is a current MLB LHP. The first question asked by the coach was "What pitches do you throw?". My son started down the list: 2-seam FB (primary pitch), 4-seam FB (when he needs the gas), cutter/slider (best out-pitch), split change (equally filthy), "show-me" curveball and a newly-acquired cut-fastball (which is honestly a pretty impressive pitch).
...and the coach's first question: "Why do you throw that many pitches?". My son's reply: "Because I can.".
As you might guess, the coach's immediate reply was that he needs to eliminate some pitches and focus on mastering the best three. We had a conversation about this when my son came home and while he understands the coach's point, he doesn't want to dismiss the other pitches he knows he can throw well.
I can see both sides of the discussion. In a game you will rarely need more than 3 pitches, but what happens when one of those pitches isn't working on a particular day? It's always nice to have another pitch to substitute in place of the other. My son has always had a very good feel for pitches and with the exception of the circle change (which he has never been able to master and the reason he throws the split change), he needs only a few sessions to excel at a particular grip.
So now I'm asking the board.....how many pitch types is too many? All replies are welcome!