Lithium Ion bateries will wear out with or without use. You should be
expecting no less than 1 year and no more than 2 years of life from
these bateries. They have the best energy density in casual use today,
at some cost in longevity compared to NiMH. You should be aware that
dSLRs with Battery grips that use AA bateries, only get a few dozen
shots from a handfull of AA batteries in the grip, compared to 1000+
from the standard LiIon cell.