I've had a K frame forcing cone crack on me. That's the weak point on the K frames and it ain't no "internet legend". I wouldn't worry about it loosening, not with MY use. Yeah, if you fire 100K rounds a year, you might wear it out, but hell, I could say that about even the uber strong Rugers. Any gun has a life expectancy before it's gonna need attention. I've never worn a revolver out, I can tell ya that, not even a J frame. I did have that forcing cone crack, though, and had to have the gun rebarreled. They claim it can only happen with hot 125 grain .357s, but it happened on me while shooting WADCUTTERS in a M10 .38 special! I had a M19 for a while. Sold it because I wanted another gun and it wasn't all THAT uber accurate, plenty acceptable, but not a real gem. I never had a problem with it, but only had about 2K rounds through it and that was mostly .38.
I like K frame guns, though, for carry afield, lighter and easier to tote than GP100s and L frames and just as capable of fine accuracy. They won't hold up to the amount of use that the heavier, stronger guns will, but how many of use shoot ONE gun that much? If you do, don't buy a K frame, get an L or N frame .357 and don't worry. the forcing cone may crack some day, though. That incident sorta put me off, but hell, the gun was built in the early 60s. It's not been fired all that much. Wharton county sheriff owned it and my grandpa traded him out of it. I know the history of the gun, fired little, carried a lot and not even carried much when my grandpa got it. He kept it for home defense.