If you are over seventy you should maybe consider whether you actually need an annual insurance policy if you only make use of it one or two times a year. It may be more cost effective to do away with your annual policy and replace it with cover for individual trips. Annual cover for those over seventy could prove to be very expensive and could be hard to find. Individual cover may be cheaper because the insurance company will know where you are going at that point in time and they will have a better idea of the medical costs in that part of the world.
If you are over seventy be sure to let the insurance company know about your medical history to be sure that you are fully covered. Also, make sure that you get their quote before letting them know about your medical history or else they might bump up the price.
You may even find it difficult to get yourself covered annually, more insurance companies may offer you individual cover for separate trips. Whatever you eventually decide to do I would always recommend that you get some kind of cover and don’t just rely on luck. It is extremely important to have some kind of insurance when you travel just in case you need to be returned home because of some kind of medical emergency.