it will definitely have begun to self-discharge and form lead sulfate crystals.
I keep a Ctek or equivalent maintainer on every battery except the one in my daily driver. I have all AGM batteries and they hate to be discharged (except the ones so designed).
GatorJ 1996 300ZX NA 1970 Fairlady Z 2006 Ford Escape Hybrid 4WD 1973 VW Super Beetle Sports Bug