I'm with NFU and have lifetime cover for both dogs, £60 excess per claim, and can claim up to £4K for each and every condition every year (not £4K to cover everything each year) with no time limit on the number of years you can continue to claim for any condition/illness. I pay a total of £67 per month for the 2 dogs.
William costs about £45 per month. He's 8 and I claim about £200 per year for Optimmune Ointment and opthalmic check ups for Dry Eye, which is a lifelong condition. I had to pay the excess on the very first claim 3 years ago but haven't had to pay it in subsequent years. I've also claimed for other things over the years, around £2.5K in total, much of it when he had a MRI scan and physio and hydrotherapy when he was diagnosed with lumbosacral disc disease nearly 4 years ago. I couldn't change William from NFU even if I wanted to (which I don't) because nobody else will cover his pre-existing disc and eye conditions.
Louis costs £22 per month. He's 3 and so far I haven't had to claim anything for him.
Edited to add - Louis is entire and his premium would be cheaper if he was castrated.