-Most batteries like to be seeing 14.2-14.5V(up to 15 on odysseys) from the alternator. If your alternator regulator has a set point of only of under 14V your batteries aren't being fully maintained by the alternator and it will shorten life some.
You would be hard pressed to get voltage that high on a newer alternator/regulator system, unless the batteries are low on charge. The newer regulators are smart and typically keep the voltage lower on charged batteries to prevent overcharge damage. You should never see voltage lower than about 13.4v with your alternator providing power. Of course, the batteries and most alternator systems were not designed for large sound systems.
Voltage in the mid 11s is not uncommon on a good uncharged battery, but as Polarbill mentioned, a battery should hold a charge over 12v (assuming no parasitic or system draw) for weeks after being charged. I am somewhat anal about battery voltage due to how bad batteries can play havoc with diesel trucks and newer PCMs. The older engines are much more forgiving on weak batteries and charging systems, except when you need to start and all you get is clicks!