I didn't fully flesh out how long these two have been at it but "well more than several years" was the idea. I really like your take on this game actually taking place over several years, too. I saw it as taking place sequentially day-by-day, but given that it loops forever, it very well could take place over several years, which ties the two together quite nicely.
Insanity is more a theme of this as percieved insanity, given that these two are, effectively, in their own mini-community entirely divorced from a human one, but still living parallel to it. Now they're trying to navigate and rediscover how to live knowing they can never die, which definitely looks like insanity to "normal" people, but makes entire logical sense to themselves.
This is part of an universe of games all about being granted immortality and how people handle it, which i'm hoping to focus on more heavily in the future: https://itch.io/c/4016065/immortal-starstreaker. Most of this game came about from wanting to write an immortal who actually liked immortality, compared to many of the others I'd done who absolutely do not.