The telescope ran out of coolant in 2009, but it continued operating for quite a long time after that. The article says that one of the biggest concerns is the

The telescope ran out of coolant in 2009, but it continued operating for quite a long time after that. The article says that one of the biggest concerns is the difficulty of communicating with it, as it falls further from Earth in its Earth-trailing orbit. Compared to the 2.5-year mission specification, its lifetime was long. I know NASA over-engineers, and extends each mission as long as some hardware operates (see Opportunity), but that's still an impressive mission lifetime.