Real World Battery Life

Now that the 830 has been out for a while and the software has been updated, what kind of battery life are people seeing? How is the battery life affected by leaving the screen visible and using navigation?

I ask because my 820 is advertised to have 12 hours of battery life, but it has never come close to that.  I have seen battery life as short as two hours while in battery saver mode and as long as 8 hours with the screen on and using navigation.  Normally I can expect it to go into battery save mode after about 4 hours.  This battery life is unacceptable for all day gravel and MTB rides and I have no choice but to replace the 820.  The decision between the 830 and one of the Wahoo units will mainly be based on battery life.