We looked really hard at it a few years back, after our 3 year old Aussie passed away from a very rare genetic abnormality - invested almost $10,000 (x-ray here, blood test there, exploratory surgery, etc., etc....it added up over time). There was only one company that seemed to be trying to offer a fair deal, and they are now gone. At least they were honest - the older the dog got and therefore the chances that expensive care would be needed, the more expensive the premiums would be.
The amount invested in insurance over time would likely cover many/most expenses anyway. And if your dog doesn't need it, then you win!
Harder to advise once you have already sunk a fair bit of cash into the insurance. But a truism from a business class years ago - never evaluate based on what you have already invested in a project. That money is gone. Evaluate on the merits now and going forward. If it is still a good deal, then go for it. If not.....
2012 Ford F-150 Eco, Max/Max
Jayco 26.5 RLS, Reese Sidewinder