Been running the same XT rear mech for 3 years now and it doesn't shift as well as it used to, it is a top normal (spring pulls mech up to lowest gear ie biggest sprocket) and the spring doesn't seem strong enough now. Shifts fine when I change up ie pull cable but not when I shift down ie release cable. have fitted new cable, checked, cleaned and lubed shifter, checked alignment of mech hanger and mech, cassette and chain are worn but not badly, still life in them but will be replacing this week before any slipping etc. Any ideas??

Yes they do wear out. It's the only way mine die normally. Take hold of the bottom of the cage and wiggle it towards and away from the bike. Much slop in the pivots now? Mine normally take more than 3 years to go like this but obviously YMMV.

They do wear out, yes, but the jockey wheels wear faster and go sloppy. I'd bet your mech would feel almost like new with some new jockey wheels in it…. 🙂

I was about to say the same thing! ^^^^

I've had jockey wheels that are practically circular after a couple of years.

In the spirit of black catting: I've got a 9 year old deore mech that periodically goes in the ultrasonic cleaner with white spirit, is soaked liberally in 3 in one, wiped clean and performs faultlessly…

But I also have an XT one which after 18 months is so wobbly I cannot persuade it perform consistently. Irritating.

Jockey wheels wear and you can replace. As above the pivots and joints we over time making it "sloppy" so the shifting isn't as good. Depends on where you ride, in what conditions and how often but I normally get about 3 years out of a rear mech before I decide that it's time to change. THe last one was replacing an XT with a deore, I was amazed at how much better the deore was, simply because it was new.

+1 for "sloppyness" over time esp if you keep geting rock strikes etc 🙂

Have already replaced the ninja throwing star jockey wheels, didn't improve the shifting, will do the wobble test tonight when I get home.