Pitch count is needed but imo should be co-registered with signs of fatigue. The signs of fatigue is debatable but I think it can be done in an objective manner i.e., breakdown in pitching mechanics/sequence or technology such as wearing a motus sleeve. I think 50 pitches for kid in a solid pitching program and 15 to 20 pitches an inning with no signs of fatigue is cruising. Whereas a kid who pitched 45 to get out of a 30 minute inning, who is both mentally shot and winging balls tells me to stick a fork in him (not literally).