Estel: I couldn't agree more with the N900-being-self-sufficient concept.

Now, as for power - I don't power down my phone - but I also charge have a VERY strong opinion that I should be reachable even in the middle of the night by those who might need to. I find that on nights that I don't charge my N900 though, it lasts rather well. I.E. not-noticeable-energy-drain.

Now, I have no doubt that the N900 would save slightly more energy being off, but without too much stuff running in the background it's not a gain that's important enough for me.

But meh, personal preference.