I stopped taking it because the evidence wasn't there. We were going to take our dog off it too but interestingly, the vet said it is still considered to be beneficial in their world. So if it's working for your sample size of one, go for it!
I've taken glucosamine for a number of years. My doctor endorses it for me because I can't take the typical pain killer / anti inflammatory things (they conflict with my blood thinner). He agrees that there are is no quality evidence.
I rebel against it once in a while and might again when my brother stops being able to get it at manufacturers cost.