When the forcing cone wears, you just have a new barrel put on.
Seen a few 19/66 that had wear or split.
Consider it the cost of having fun. You shoot that much youve sent a good chunk of money down range
Barrel replacement should then be an acceptable cost IMHO.
4" .357 magnums are annoying in blast.
6" considerably more polite IMHO.
Think a 66 looks best as a 4" though, and a 686 looks best as a 6".
If one likes to run 38 spcl.....get a K frame
If mags your normal fodder, get the L frame.
The newer models supposedly stronger frame but they got some changes that hurt resale ( lock and other ).
The old stuff fetches silly prices
The key advantage to the L-Frame is the thicker, more heavy duty, forcing cone. They likely didn't need to make any other part of the gun more heavy duty to accomplish what needed done.