After purchasing a used Mod 36 (1983 manufacture) last week, I asked S&W the same question and received the following reply from Customer Service;

"I wouldn't shoot +P out of that gun. Generally speaking even with our newer Model 36 that can shoot +P we tell customers to not put a steady diet of that ammo because it does put a lot of wear and tear on the gun. +P Ammo is a very hot and over pressured round."

FWIW and YMMV