In high school my son almost always ran poles after the game. Don't remember how many, at least several to a dozen. In college he is doing sprints. This goes along with an article I read in a college baseball publication that distance running does not help develop the explosive muscles needed for performance on the mound. The theory along these lines says that the action of pitching and fielding the position requires short bursts from the legs and other muscles of the body. Long distance running is contrary to developing this explosive energy. Think about it a little and it starts to make since.
As far as how many/far; I would say that is probably different for the level you are playing at. 12u to 16u will change. Above that should be pretty consistant. Younger players should be good between 10 to 20 sprints that should vary from 40 to 80 yards depending on how much mound action occured. Over 16 I would say 15 to 25 sprints from 60 to 100 yards. In any event IMHO, working up a good sweat and mixing in poles and a little distance running right after the game is a good thing.
Don’t shot the messenger on this one. I always thought long distance running was the right thing to do after pitching. But I believe there is some changes occuring in this line of thinking/ training.