Severely discharging and leaving the battery discharged can cause harm and shorten life in AGM batteries.If you're not going to use the battery for a week or more at a time, we highly recommend a charger maintainer (also called a trickle charger) to keep the battery from discharging.
Keep the battery as fully charged, as often as possible. No, these batteries do not develop a "memory" like some nickel-cadmium based batteries. Severely discharging and leaving the battery discharged can cause harm and shorten life in AGM batteries. Have you heard about sulfation? It's not pretty stuff.
Let your batteries sit unused for the winter months. Even if you start your motor or engine every once in a while, it still doesn't make up for the time left to drain and sulfate. No, letting your batteries go without a charger for a single winter won't guarantee a dead battery in the spring, but it will guarantee shortened life span.
An AGM battery is designed to be charged slow and low, and overcharging it can kill the battery itself. So, a normal battery charger can't be used to charge an absorbent glass mat battery.
Nevertheless is the agm worth the extra money? Short answer would be no, not for a street car. However theoretically AGM actually dissipate slower than a conventional battery and again theoretically they can bounce back from discharge easier than even a deep cycle (time to full charge but not number of discharges).