In reply to purplemonkeyelephant:
Look in my posting history for some of my experiences with pet insurance...
A lot of policies do promise not to up their premium until a certain age, but that's generally around 6 or 7 years, and if you've claimed then that promise is dropped anyway.
What is not clear at the outset is that you are essentially binding yourself permanently to the first insurer you go with, because if you ever change to another then anything that's been treated in the past is regarded as pre-existing and therefore not covered. I despise Ginny's insurer (Bought By Many / Many Pets) after they played silly buggers with some of her treatment costs, but there's absolutely no possibility of changing. They are, grudgingly, paying out on most of her anxiety meds, which she'll be on for life, so I will have to stick with them.
Pongo is with Purely Pets, who have the most atrocious communication skills, but do seem to actually pay out in the end.
As I understand it, PetPlan is one of the most expensive - they cover more, pay promptly, and are better at not trying to wriggle out of paying, but you do pay for the service.
Assuming you have the ability to cover an unexpected bill, going without medical insurance is definitely an option and especially as they get older and the premiums increase, it may well be worth the gamble.
I would never recommend this to anyone who couldn't guarantee being able to lay their hands on, say, £5k, at very short notice, for emergency surgery. Or at least who could stomach having to say that they cannot afford surgery so the pet has to be put down.
If you do go this way, as suggested above, get third party insurance from the DT.
So to actually answer the OP: keep going for now, but give thought to dropping it if/when the premiums get too high.