I also want to know if batt life is any different between 'track up' and 'north up.' I speculate that the redraws for 'track up' consume more power, but I don't know if that impacts battery life. I have the later generation of your GPS, the eTrex 30, and battery life is probably close to the quoted 24 hrs. Before that I had the HCx, which seemed to have comparable battery life. I think the biggest suck on the batteries is the backlight. Anyhow, I poked and asked around in forums about track/north-up battery life and never got a response. I don't have time to do a controlled study either. I'm just planning on leaving the GPS in 'north up' [which is what I like anyway], carrying spare Li batteries and [hopefully remembering to] shutting it down at night and/or on sections when a GPS isn't needed.
PS - One nice thing about the 30 vs. the HCx, I can load one track [like Toby's CTR track, thanks, Toby!] instead of having to load smaller 500 point tracks.
does battery life get extended (or consumed) depending on what screen is being displayed?...