Agreed Flying Binghi, should have been clearer that I don't believe that Airframe Fatigue played a pivotal part in this incident, from the report it certainly seems like it just ended up Over-stressed in a CB.
But the age and hours wouldn't have helped either in my mind and anytime I'm flying in IMC these days it's a thought that crosses my mind or whenever someone tells me a story of that horrendous storm they went through in the same Aircraft. It's enough to remind me that without a WX Radar you just can't really know what's sitting inside those clouds once you're in and as others have pointed out, even with one you can't be 100% and I don't want to be the one that finds out about that crack that's been forming for the last 10 years in an unseen corner of a wing.