"provision of a free email address years after one stops being a paying customer is rather generous in this day and age."
It certainly is. Although here in Ireland, I still have an @eircom.net email address that's active - 17 years since I was last a paying customer of theirs. They've been through a name change since then too.
I generally use it as a throwaway address to register for all sorts of shite, and maybe check it once every two or three months.