I do almost the same thing with Dancer, but we use tagamet instead. We use Springtime Inc also, along with some other supplements. I also have Arnica on hand and if Dancer plays rough or gets bumped too hard, she gets a dose of it. As far as I know, Dancer has never had Rimadyl.
Dancer is 12 also.
I agree with seking chiropractic and acupuncture treatments. You can search here to see if there is a Acu/Chiro Vet near you.