I'm a bit new to the Garmin family, even though I had a VA3, for about 18 months, it never had any sort of "battery saving GPS mode", such as UltraTrac.
We do a yearly "mini tour", for the 4th of July, sort of just a quick loaded (touring bike) ride, it's only 20-25mi/way, but my bike has my "regular touring load", so it's pretty heavy, carrying almost all the "group gear" for the family (maybe 125lb or so, including the bike itself).
Anyway, part of my purchasing decision for the 945, was to "retire" my Suunto Ambit3, and still be able to use a "low-battery-drain" mode, such as UltraTrac (on the Suunto it's just a low-sampling-rate setting).
I figured with 60 hours, I could use it daily, when touring (typically not having access to a charger, sometimes for days in a row), much like I used my old Ambit, I could easily ride a week with it, with very good accuracy, still.
However, when I did my first two "test rides" this past week, with UltraTrac on, my actual measurements were basically "useless", it seems to have maybe a 30-35% "accuracy", and otherwise it simply thinks I'm not moving, at all, for very large parts of the ride (the link shows 7.43mi, but in reality, it's about 22-ish): connect.garmin.com/.../3816075064