Hibernating way before timeout, while sleeping (S3)?

[PGrey]

I'm seeing some really weird behavior on 14393.67, with regards to sleep(S3)/Hibernate(S4).

I'm set to sleep (S3) at 25 minutes, and everything else is lined up before it, time-wise (drives, screen, etc). That all works fine, more or less, like it did before, or if I manually sleep it too, it goes to S3.
However, if left alone more than a couple of hours, it decides that I really wanted to Hibernate (S4), even though my hibernate(S4) timer is set at 1440/24 hours.
I'm not sure how fast it's doing this, I think it's about 2 hour-ish, but the event logs don't show the trace (S3->S0->S4), like you would expect, they just show the initial S3 state and then the wake, very strange stuff.

This used to work just great, my machine would sleep overnight, as expected, but if I was gone for a day or so, and forgot to hibernate it, it would go to S4, just fine, on its own, at least most of the time (sometimes this wouldn't happen, but oh well, things occasionally block sleep states, such is life).

Going to hibernate, seemingly randomly, after a couple of hours is a big problem, IMO, if it's unintentional. Something is clearly wrong in .67, in this area.
I thought it was just me, but my wife asked me about her desktop today too, was wondering why it was doing the same thing (hers is set to similar 1440/12hrs. Powercfg is useless, it has less info than it ever has, and my sleep-study is fine too.

Anyone have info on why they changed this, and if there's a known-issue?

 

[PGrey]

Update, I finally caught a Sleep(S3)->Hibernate(S4) in the event viewer.
No real data though, just an: Event 42: The system is entering sleep. - Sleep Reason: Hibernate from Sleep - Fixed Timeout.

Interesting, because my (actual) fixed-timeout is still 22 hours away, this was almost 2 hours exactly, from when I'd gone to S3.