Like most, I use 2 devices.
Samsung Galaxy android phone - for Descriptions, Hints, and Logging on the trail
I run it with the GPS off and in flight mode (no Data) using a PQ for the information
Massivly extends the battery time.
Then I have an ETrex H - for a more acurate fix at the GZ.
Bought a spare battery for the phone for less then a Fiver! Well worth it!
TheBoySmythe