My only STI failure was on a single bike with Shimano 105 (late 90s era). I had them on the bike I used for training and was doing a lot of riding in the rain. The shifting degraded and eventually the shifter became useless.

My racing bike has Dura-Ace STI, no problems except it does get more finky after a wet ride. It's more of a cable grime issue than STI though. Gore-Tex Ride On Cables helped that.

I've burned up several XT rapid fire shifters riding in wet conditions so common here in the PNW. Now my weather mountain bikes all sport thumb shifters.

I did get a chance to ride a Campy Ergo equipped tandem recently and was very impressed with the shifting. I like that the brake lever IS a brake lever.

All that being said, our new tandem will sport bar end shifters. They work great, they aren't fussy and they are very durable. I have a pair that has survived at least 3 bikes. Put them on, forget about them.

This is less tandem applicable but on my bar end equipped touring bike I can scavage any 5-8 speed wheel that will fit in the frame, adjust the derailleur and switch to friction mode and I'm back on the road.