What sort of mileage has the bike done?
I had mine changed at about 30,000 miles, but others on here have simply not bothered and put up with the rattle, which is a debate in itself.
Whether mine actually needed replacing, i don't know, maybe it was in between clicks?
At the time i just couldn't hack the noise as i have sensitive hearing and it was driving me mad, so i just got it done anyway.
And i can't remember how long after being sorted that it rattled again, but i do know it hasn't done it for a couple of years now.