Steve, i have planned everyone in my head the exact way you are saying. i use to rent out property in the UK so i was doing my own tax returns, this gave me access to all my tax information over the years. I had a look last year and i have enough credits to qualify for the full state pension now even though i am only 58. So leaving the UK at 60 for the Philippines with plans to come back once a year to visit family and friends. Will be living off my private pension until i am 67 and then will reduce what i receive from my private pension for tax reasons like yourself. Just what you have planned as well.
Going off that you have said i would be wasting my money paying more N.I. contributions once i have left the UK.

I am in very good health at the moment but i know things can change quite quickly so on that front i could not be taking out a crazy medical cover in the foreseeable future. Might think more about it once i get in to my early 60's.