It depends on your dog really. I would still put my 11-year old lurcher through almost anything as he is as fit and healthy as a two-year old. However, what the situation is in another year or two, I don't know.
My insurance premium for Dylan (said lurcher) is now £106/month, so around £1200/year
I have decided to continue with it as he has a couple of pre-existing conditions which could become very expensive if something went wrong!
If it gets to the stage where major surgery may not be an option anymore, then I might consider changing insurance policies to something cheaper, which of course that would mean that pre-existing conditions are excluded.