It is hard to find strings that sound better than a fresh set of D'addario strings. The quality of the sound is unmatched, I would say, at this price point.
With that said, the lifespan is not the longest. I find that after a month or so, most of the brilliance of the tone is gone. However, they rarely break. I've had a set on my guitar for probably five months (for rehearsal). Just the tone; it degrades fairly quickly, which other brands might be better at, but for double the price.
I would rather buy two set of these instead of one more expensive.
Recommend!