I noticed the same thing. Also, I noticed if I left the game i.e. logged out, when ever I logged back in my stamina was still where I left off. Even days later.
I think this is due to the fact that people took advantage of going to DR to re-up their stats or log out then back in for the same purpose and believe that this is the way the problem was solved.
I have no problem with this personally, but it would be interesting if there was a sleep mode you could go into to regain your stats. It could go with the in game time......or you could just stand still and talk to people.