I have fired about 2,500 std pressure range loads from my Airweight 637. I enjoyed it very little. I have also fired a few dozen +p rounds. I enjoyed none of them. In fact, I fired five of Cor Bon's 115gr JHP +p (no longer offered, thank goodness), and swore I never would do that again. The remaining 15 cartridges are now delegated to my 686+.
My point is twofold: Airweights kick hard, even with range loads; and mine is still in near-mint shape. Most of the cracked frames came early in the production cycle. And S&W has the best customer service in the business. You break a 6xx snubby, and they will either repair or replace it, free. Including shipping both ways.
Cordially, Jack