I have been using the hobbyist licence for Eagle for several years now after being a KiCad user and admittedly I don't use Eagle every day, and in some cases for weeks at a time. When I do start a new project, as expected, I use Eagle daily for perhaps a month at a time as I modify my circuits and and create new pcbs. I still use v6.5 and have not upgraded only because there is so much negative controversy going on regarding recent and planned changes to the licencing scheme (moving to subscription based) and I don't want to be a potential victim of signing up to software that from a monetary aspect - is overpriced for hobbyists as I can always revert back to KiCad which is getting better all the time.
But I do have a very annoying problem with my current version - after some extended time of non-use, Eagle asks me to re-enter the licencing credentials - the file key and associated code - I am using Windows 10 and nothing has changed with respect to my computer set-up - there have been no hardware changes and it does this on a regular basis. Why?