I am pretty sure I once read that in order to get the full benefit/ratings bump from spring training, a player needs to have 25 plate appearances (and more than that is pointless). Unfortunately, I don't recall where I saw this, and I'm not sure how valid it is. Does anyone have any input on this?

Also, is there a similar magic number of innings for pitchers in spring training?

I'm looking for the answer to this too.

I thought it was 30 AB and 10 IP

I don't recall anyone having more than a guess. There've been numerous theories floated but I don't think I've ever seen a number or approach that's known to maximize development/minimize regression.