I came across this full-timing couple and their write-up on their expreiences with LifePO batteries.
http://www.technomadia.com/2015/02/living-the-lithium-lifestyle-3-5-year-lithium-rv-battery-update/
Lithium Iron Phosphate batteries are not the same as lithium Ion batteries that have all the safety concerns.
They are claimed to be safer than lead-acid with many advantages.
-easy charging requirements
-Fast charging (3 hours or less)
-Light weight (100Ahr @ 12V weighs about 30lbs)
-80% depth of charge (compare to 50% and less for SLA)
-2000+ charge cycles
-does not need to be kept at full charge
-high rates for discharge allowed with little loss of charge capacity

Only thing against them is they cannot be charged when below 0C and cost (about $680 for 100Ahr 12V)
I installed a new set of two 6 volt golf cart batteries (made in USA) in spring 2013. This spring the measured capacity was 63A/hrs so I pulled them. I run a all electric fridge so I know I pulled them below 50% a few times. Pulling a lead acid below 50% charge really shortens their life.

Opinions/experiences?