You want to use a good battery MAINTAINER. A cheap trickle charger just provides a constant current. Smart chargers apply current, discharge surface charges that accumulate on a charging battery, and then re-apply a charging current. Charging a battery to full and allowing it to sit is OK if you use them frequently.
I've been told leaving batteries on a trickle charger when not in use is the best way to get the longest life and optimum charge out of batteries. I've also been told charging them fully after use is fine too as long as they don't sit more than a month without another charge.