1) On/Off Reliability: Sounds like your power button is not making good contact and I would maybe see if your local store or customer service will switch out the Nook for you under warranty. However I would like to point out that you do not need to hit the power button to take it out of sleep mode. The Home Key (the nook symbol click button) works to wake up the nook.
The power button itself has several "modes". One click should put the nook to sleep and wake it up. A 3-4 second press will begin power down and start power up. A 20 second press will perform a soft reset (powers down and clears caches)
2) Brief Battery Life: Here is the Nook HD spec sheet.
It states "up to 10.5 hours of reading" and "up to 9 hours of video". The footnote then also states "Battery life depends on device settings, usage and many other factors. Battery tests conducted using specific units with Wi-fi off and power save mode on. Actual results may vary."
I would have to say that if you are getting 8 hours of reading time then that falls into the realm of "normal" and has been discussed on these forums before. The statement you mentioned about the sleep mode for several weeks is exactly that, sleep mode only. I'm assuming that statement alludes to the fact that you can set your nook down and come back to it in a few days and still use it right away. This seems to be the norm for tablets in general. Now if you are only getting 2 or so hours of use out if the nook then that would be a problem.
General power usage tips:
1) Sleep mode is okay if you use the nook all the time and want to just jump right back in without power up each time. I would power down every once in a while (once a week?) to restart the software.
2) Power down if you know that you will not use it for a while (several days).
3) Keep wifi off if you are not actively using the internet. I keep my wifi on all the time but then again I plug my Nook in to charge up every night.
4) There is a power save mode listing in the settings page. This seems to limit the brightness of the screen which can also save power.
Hope this all helps you.
It really sounds like the OP may have bad behaving app(s) that are both causing crashes during sleep (evidenced by having to restart when trying to come out of sleep) or battery usage (i.e. they are trying to communicate to a server of some sort periodically, and even if WiFi is off they are active and trying to do this). There a number of posts on some Android forums that discuss this, although I haven't seen any on this forum (although I might have missed them). The recommendations are to ensure that no app is set to receive notifications, such as weather updates, etc.
Discussions mainly in Battery Life threads - here are some;
PJLLB, thanks. A friend has an android tablet (not a Nook) and he can press one button to stop all applications from updating. But I think I am right in thinking that on the Nook HD one has to go into "All Settings" > "Account Settings" and then set "Auto Sync app data" to Off? I have all notification set of Off. But I can't see any other way of killing apps. I downloaded and installed "Advanced Task Manager" and set it to periodically kill all those apps that keep springing into life, but I have no idea if I am exploiting its potential. Being used to controlling Windows, I find it crazy that in the Android world applications apparently just keep loading themselves!
I too occassionally have the "wake up, sleepy head!"problem, but not on a regular basis. I use the Home key every time I wake it up. I'll have to monitor apps to see if any might be the culprit. Battery life is fine. I use Battery Doctor and Clean Master on a regular basis to close apps and clear the cache. I sometimes touch the power button to put it to sleep, but not always. It's not a dealbreaker for me, I love my HD.