Anyone have experience with lithium batteries and GPS? I want to go on a 100 mi.

[QuestionsGPS]

I've been thinking about later going on a 100 mile hike through the Uinta Mountains in Utah, the Highline Trail.  To make it less of a hassle in changing the batteries, especially if my hands are greasy when going through all that backpacking/camping, I've heard that lithium last longer than alkaline/rechargeables? 

Has anyone here had much experience with lithium in their GPSr?  By the way, I have a Garmin Oregon 450, an energy guzzler which is rated for 16 hours on the specification sheet, but really only 10 hours if you don't have the screen set to turn off after you haven't touched it for a couple of minutes.

I've seen both the Energizer Advanced and Ultimate Lithium batteries at Walmart, but I'm not sure how well these work, and to what extent it's advertising hype when they say lasts "9X" longer than ...."  I'm not sure if they set up their numbers a certain way to make it look good, like a lot of advertising does.  The batteries I use right now are 2500 mAh AA rechargeables, so I don't know how they'd compare.

[schweady]

I use Energizer Ultimate lithium exclusively in my Garmin 62st. Yes, they do last 8-10x longer than regular Duracell, which used to be my go-to for most devices. A fresh set will give me at least 2 days of use while in the BWCA, running 8-10 hours per day.