Windows 8.1 Pro 64-bit fully patched fairly new (this year) HP laptop.
After extended sleep (an hour or more, whether on fully charged battery or plugged in), laptop takes much longer to resume (almost as long as a cold boot) than it does from a short period of sleep (less than an hour or so). First the symptoms of a normal, "quick nap" followed by those for the abnormal, "long nap."
Quick Nap (Normal):
- Hard drive light blinks
- Power button light blinks
- Pressing the power button wakes system
- Resume takes seconds
- System log indicates the system resumed from a low power state, and that the wake source was the power button
Long Nap (Abnormal):
- Hard drive light stops blinking
- Power button light stops blinking
- Pressing the power button resumes system
- Resuming takes almost as long as a cold boot
- System log indicates the system resumed from a low power state, but that the wake source is unknown
Hibernation is disabled on my system, as it was out of the box.
In the past, with Windows 8 and 8.1, before the Windows 8.1 Update patch, I was able to sleep my system for hours, even a day, and have it resume in a few seconds.
My system is Energy Star certified, if that matters.