My wife has been carrying her M36 for 32 years now. First as a BUG, then as a primary for 22 years as a detective. Dept regs specify the 158grSWCHP +P load. She is allowed to use the same load in non +P for quals, but has been using the +P for 29 years for everything. She shoots 200 rounds year quals for regular, and for the same time has been required to qualify with both primary and BUG monthly as she is SWAT (talker). Every so often we go to our club range and she goes through about 100 more rounds of +P(she isn't too big so she figures she better be able to shoot straight).
She has at least 10,000 rounds through the M36. 5 years ago i sent it back to Smith for a action job and refinish as a present. It needed no extra service(I made a point of asking), no stretching, battering or anything. Now that particular "FBI load" is not particularly punishing in terms of pressure, but it is pushing a heavy slug at respectable speeds, and it most definitely is rated +P for a reason. I suspect the steel J frames can take a lot more punishment that most folks think.