I find the opposite to be true, and manufactures for new cars with AGM tell you to disconnect them if car will sit for 2 weeks or so.
The Lead Acid Interstate in my 70 RR never needs a charge and works great. The AGM and Resto battery, will not hold charges if left too long, especially with a small drain, like a clock.
I believe even Modern Optima techs state occasional recharge with correct charger required.
I disconnected this AGM battery last August ('16) and did not put a trickle charger or battery maintainer on it from that point. I also did not charge it before or after I reconnected it two days before the Norwalk, Ohio Monster Mopar Weekend.....it fired up on the first turn of the key and we (family) have used the '69 GTX every Saturday and Sunday (and forgot, each Wednesday for the local Advance Auto cruise night) since that Norwalk weekend. So far NO problems with an AGM resto battery. I will NEVER, EVER get a flooded battery of any type for my vintage Mopar after a bad voltage regulator cooked the vintage flooded Mopar battery and ruined the under hood and engine compartment paint on my '68 Road Runner.