I have put deep cycle batteries in my trucks with winches (huge current draw) for years without any issue. Sometimes they are secondary batteries and sometimes as the only battery. Most auto voltage regulators charge in two stages, Bulk charge for the first few minutes after startup and then a trickle charge after that. From a charging perspective it is more important if it is a lead acid battery, gel cell or AGM than if it is a deep cycle or not. Gell cells and AGM have different charging characteristics. Charging a gell or AGM battery with a voltage regulator designed for a lead acid battery will reduce the life of the battery due to overcharging. In most cases probably not enough for you to notice.