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You know, SP's are "supposed" to get knocked out once in a while anyway, have a 50-pitch outing that bloats their ERAs but freshens their arms.
30 starts times 5-6 innings, subtract five disaster starts, you can keep a pitcher at 150-170 innings if you believe this to be necessary.
.........
As James said, there isn't a lot of reason to believe in the arbitrary 150-IP limit, but you can't oppose accepted dogma with intuition.