Anyone know if there is a command to set a power down after a period of time?

Yes, with ARM CPUs, powering down is basically the same as sleep mode, so it's the timeout for your backlight.

Is the N810 considered to be in sleep if the screen is off? I was surprised to see how long this thing takes to start up. I'm trying to run it via some solar panels during my trek so I can't waste power by having it on all day but I also don't want to waste time with a 2min start-up. Most laptops/computers have a sleep mode but I can't find such a setting on the N810s.

The ARM CPU will go to basically zero power usage if it's not being used, this is instantaneous, so there's not need for a laptop like "sleep mode". You should never really be turning the device off, just stick it in offline mode and lock it when it's not in use. It'll stay powered for about a week in that state.

Cool, thanks for the info. Now I need to find a nice (cheap, light weight & long lasting battery) WiFi detecotr so when I wander through a village I know whether or not to whip out the tablet.

I like to listen to Internet radio upon retiring for the evening. So what I'm asking is if there is a way to power down the N770 after a certain period of time not just turning off the screen since Internet radio streaming still continues until the battery is depleated. To put it another way I would like to find out if there is an equivalent to the good old fashion sleep function found on most clock radios?

Just do

after some time or if you still want to power down

should be working... even poweroff works i think.