I was doing some battery research over the holiday myself. I'm gonna start a new thread on a specific issue with rechargeables that people need to be aware of, but trickle charge is simply the charge to keep the batteries topped off. However, the best purpose for trickle charge is to keep your batteries in peak shape when they're not in use. You can leave your batteries in the charger 100% of the time and trickle charge will keep them in optimal performance condition...IOW you can leave them on trickle for a year and the batteries will still be good as new. The reason is that the trickle charge keeps the chemicals inside the battery optimal for battery performance This of course assumes that the trickle charge is the proper voltage for the batteries, so since your charger is specifically designed for these batteries, I think you're good!
EDIT: Above discussion on trickle charge is applicable to SLA batteries.