NiMH or Li-ion trickle charge?
To my knowlegde Li-ion cells handle incomplete charging cycles very well. If you're sure to be able to provide comfortable temperature for the cells (0-40C or 30-100F), there is no reason to expect them to have a short battery life. Li-ion cells wear out quickly at higher temperatures, and should not be charged when cold (although discharge is OK).

Ni-MH batteries have a broader temperature range, but don't like to be recharged without a near full discharge first.