Originally Posted by
milkbaby
Don't quote me on this but Shimano came out with (I think) ST-5601 for doubles and ST-5603 for triples after people had problems with the original 5600 design.
That. Sorry for quoting.

See your LBS for a warranty. I toasted two before getting the double specific shifter. I did get around 20,000km on the 2nd.