Going with similar arguments on various forum threads, and having a bias against using closers myself, I shifted most of my teams having the whole bullpen on either setup A or setup B (it seems, correct me if I am wrong here, that unless the setup A pitchers are worn out, setup Bs usually come in only when your team is losing).
But I found that in a lot of these teams, even when I had high IP pitchers (Steele, Nehf, Toney, Ramsey, Potter, Berry, Beene - often at least two of these) that the entire staff went into blue with some in red in no time at all. When I moved say, Nehf or Steele to Long A and Bailey or Gossage or Rivera or Eckersley to closer they were back to 100% pretty quickly. This happened on three or four teams. I am aware that there are a lot of variables at work here that I haven't had the time to analyze: frequency of high score or extra-inning games, pitch count of my starters, 3 or 4 man rotations etc. but my impression at least is that this phenomenon spread through my squads like wildfire and was spent when I moved everyone back to defined roles despite my bias against doing so.
Since the assumption is that the setup man will pitch in around 70 game, closers in around 50 (if I remember correctly) and long relievers somewhere in between, I wonder if the explanation (again, if this was not coincidence) is that the SIM thinks that each of these setup men will pitch 70 games, 2 or more innings when in fact if you have 6 of them none will have to work that hard, but that overall staff situation is not taken into account when evaluating likely individual overuse?
Is this a problem others trying this strategy have encountered as well? Is there a study of it?