I was using Strava for over 5 hrs on the Daz Holloway race and my Android phone showed just less than 50% of battery power left at the end. Runkeeper has an autopause but as Stolly says it is useless off road as the thing was often saying I was not moving. So I turned off that functionality. Stefan in Pennine was commenting about the autopause on his Garmin and Wardy showed him how to turn it off, I belive it was a watch settng rather than a Strava setting but I may be wrong.
EDIT
Looks like it is a Garmin setting.
http://www.beginnertriathlete.com/di...264447&posts=8