Five or six years ago I was thinking to buy a S&W 340PD and I was concerned about its durability. So I e-mailed S&W about the my concerns when shooting factory .357Mag; they said it will hold up 25000 rounds or more of factory .357Mag. So it is pretty durable. Anyway I decided against it because of the lock, titanium cylinder, alloy frame and bla, bla, bla; I decided against the 642, 638, 442 for some of the same reasons as well and finally opted for an all steel NIB 649-1 Bodyguard of 1988-89 with all the papers and everything: I was happy like a puppy. After only 800 rounds (mostly .38SPL Wad Cutters) the hammer stud broke and I wasn't happy anymore.
After that experience I don't judge S&W snubbies on weight, materials, lock or no-lock, date of production, etc. anymore...