We used to have a bulmastiff which we bought as a puppy and insured him straightaway. At about a year old he was diagnosed with hip dysplasia (I think that's how it's spelled) The treatment would cost a fortune, but insurer paid for them. Though we had to pay the vet then claim money from insurer. We were only covered for 2 years for that condition, after which we were on our own.
When doing a job at a stables the nice lady there recommended glucosamine & chondroitin tablets (available at supermarkets for cheap as chips), pretty much the same thing. Worked a treat. Must have saved us hundreds if not thousands. Can't believe the vet didn't suggest this ;)

