N900 is great phone for its features, so if a feature is present and find a usage case for it, I prefer this feature to be on.
Currently I have 3g/WIFI auto connect all the time. I have bluetooth on and connected to my handsfree all the time. I have gtalk awlays connected. I have zaplock updating my latitude im backgrouind. I have applied varius tweeks to improve my device speed and bettery life. I'm very happy with my battery life (~40 hours), as it is better than an iPhone and much better than android devices. Both of them could not afford even the half I have.
I also notice that skype and other chat clients are draining battery. So I limit my IM accounts to just 1. I would be happy to see a tweek or something else that will alow me to have all IM on. Anyway it is not possible now, so I'm sticking to Gtalk only.

I do not provide a solution here, just sharing some info about my observations and how I'm using my device.