3-12 in one night, no that's not tough. He averages 16 per IP though, and going one or two innings three nights in a row CAN be stressful to a pitcher's arm. Izzy, Guardado, Borowski, Valverde, Wickman, Percival, Hoffman, and Nen's arm's aren't getting blown out by high fiving their teammates.
Last year in a span of 5 days, Lidge pitched 2, 2, 1, and 3 IP. This is with no rest in between, so yeah being an RP can be stressful. I'm not saying Lidge will blow his arm out, but he's being abused more than any RP that I can think of and there's nobody else in that pen to take the pressure off.
"Jack, will you call me, if you're able?"
"I've got your phone number written, in the back of my Bible."