I tried Staysure and they would only do 35 days on an annual multi-trip policy for over 70's.
I also tried Goodtogo, Insure-and-go,,MoneyUK, Saga, MPI, Confused.com, AllClearTravel, Alpha, Explore Insurance, NFU, Age UK, Direct Line, OK, JD Travel, FreeSpirit, all a for 90 day, multi-trip, over 75 policy. Only MPI (one 90 day trip only, but negotiable) came close, along with Saga (who have a max of 120 days total p.a). Most of these were for Europe only.
The only one who met my requirements for multiple 90 day trips, over 75 (no max), worldwide was Nationwide. In fact, the total cost for my annual multi-trip policy is significantly less than all of the above wanted fro a single trip policy.