I guess it all depends on how long you've had the bike , as regards to the measurements your getting .
My adjuster foot moves about 1mm every 2-3k miles.
On a tre k I believe it should last about 24000 miles. I did mine at about 18k if I remember correctly.
In changing it I checked my guides we're ok and were indeed free to move ect.
So for me changing it is cheap £30 tops and provides the clarification of condition inside with the added bonus of not having to do it for another 20k miles or so .