I recently had a problem with Elixir strings - constantly breaking on the G on different guitars and in different areas of th string. Other guitarists had reported on the same problem with Elixirs - and I didn't have this problem with, say, D'Addario EXPs, Martin Lites, etc.

I raised the question with Elixir who were sympathetic, if non-committal about the possible reasons - and mailed me a couple of free sets. I'm now trying them on a new Larrivée and, so far, have only broken a D string (but that was at a real thrash ceilidh session).