When Petplan guarantee "cover for life" that doesn't mean cover for life at the same premium 
whilst not exactly being a scam; pet insurance is more a means of ensuring that if you beloved pet has an illness or accident that costs £thousands you will be able to cover it rather than a more distressing alternative
generally they operate like an endowment; you pay in from when you get the cat at a reasonable rate; after several years you may end up claiming but often you get back less than you have paid in real terms by the time you take the excess into account. Generally they will not take older cats on as "new business" or will charge a hefty premium.
we stopped insuring our 8 year old cat when the premiums got silly. He lived to 15; the last 3 of which were on expensive but not extortionate medication (£25-30 a month) and vets bills for the usual renal failure; I never did the maths to see whether we would have been better off keeping the premiums paid up...
he did us the final dignity of croaking before we even had time to get him to the vet and is now commemorated by a nice shrub in the garden
