I agree with JTQ you need not do anything with a well sorted / inteligent charger (Lidl / Aldi being a good cheap solution) but with the much older chargers they can eventually take the volts up somewhat higher than on a car and the battery can start gassing (hydrogen), so loosening the plugs is a good idea then.
A friend's son overcharged a battery with one of these older chargers, then did the stupid thing of disconnecting the leads without switching off first. A big bang resulted which split the battery in two. Fortunately with no damage to himself.