I would never, not insure now. All six of mine are insured, as are the cats.
I would also insure from the day the bun came to me, which I didn't do I left it a few weeks, which I regret bitterly.
I am having to rehome Cherry because I can't afford her dentals. She showed symptoms 2 days after the insurance started, and rather than let her suffer I took her to the vets. She wasn't diagnosed until 4 weeks later, but because she showed symptoms, they wouldn't insure her for her dentals
I have to say it is the most horrible decision I have had to make, bar PTS Princess. And in a way even worse, because I know she will be living her life else where and in some why I have failed her. But in another I was her saviour. I
As they are already insured, they will not be covered for previous ailments if you cancel then go back.