Definitely per year, especially for younger cats.
Eg 'Per condition' - once you've spent 7k on a certain condition perhaps over a couple of years (easy with MRI's etc) then that's it, you can't claim for that condition any longer even though the cat may have 10 years left to live. 'Per year' means you could spend 7k on vets bills in total each and every year, even if it was on the same condition.
