Since it's thread resurrection week on HB I thought I'd give this one a bump and nominate it for "HB Classic" status.
At the time of Sam's OP I had two dd's very early in their pitching careers and they both continued to pitch through high school and fortunately managed to stay healthy. I don't know how much of a difference Sam's posts on this topic made for them as most of their early years of travel ball were spent trying to find teams where they could get enough pitching time rather than worrying about too much pitching.
I can't say we followed Sam's advice strictly to the letter throughout their later years. There were times when circumstances required my dd's to pitch more than one game a day and I don't know of any other pitcher in my area where that wasn't sometimes the case. The one thing we did different from most of the pitchers I know who had injury issues was emphasize a winter shut-down period where they did other sports like basketball or winter track.
My youngest dd still has her senior year of HS left and committed to a university that isn't highly regarded for softball in general and pitching in particular but if she suffers an injury at this point or beyond she'll at least be at the college she always wanted to go to. I know you've been banging the drum on this ever since Sam so I just wanted to say I heard it way back then and thanks.