I've got a pair of Shure M447's I bought just over a year ago, and I've never replaced/changed them. I don't play tunes every day, more like every two or three days, roughly twenty mins or so at a time (trying to average it over the course of the last year).

recently I've noticed that some songs don't sound too good, but I'm not sure if this is the design of the needles, or b/c of wear. I can't positively say any songs sounded better before, just curious how much wear it takes before needles should be replaced.

in any case, I've thought about replacing them w/ Ortofon CC Nightclub E's, but just haven't wanted to spend the cash yet.

if u have been using them about a year every 2-3 days then i think it's time to change em