I've tried Martin Lifespan SP strings on several acoustic guitars, all different models. I like 'em, for tone, playability, longer life. I have one guitar (not mentioning the maker) that has been so awful on various brands of strings that I couldn't believe it; it's like the strings just die prematurely on that guitar. So, it's been sitting idle in its case. Today I took it out and played it. The strings didn't have a previous hour of play on them, yet sounded terrible. I put on a set of the Martin Lifespan SPs, and that ax sung! I'm not kidding; I was blown away! Best I've ever heard that guitar sound, new strings or broken in. I'm counting on them outliving and continuing to outsound other strings I've tried on this guitar. If they don't, it's not the strings. They've held up really well on my other acoustics.