The other factor to be aware of in Medicare Supplement Insurance is that they are rated (priced) in 3 different ways...
Age Attained which means you pay the premium based on your age. It can and usually does increase on your birthday. It can also increase due to medical costs increasing in your group.
Age Issued premium is base upon the age you are when you take the policy out. The younger you are (65) the better. The policy will only increase based on increased medical costs in your group. We have this one. In the 8 years we have had it, it has increased at the most $5-7.
Community rating means the same premium is charged to everyone who has the policy. Premium can increase due to medical costs increases but not because of age. A friend has the AARP supplement and is very satisfied with it.
In my state almost all available policies are age attained rated and go up each year. In the long run, these will probably end up being the most expensive. There were only 2 that were age issued related in our area, and Trans America was the one that responded to my requests. AARP is the only policy that I am aware of that is community rated.