Your battery really is only needed for starting the vehicle, and running things when the engine is off. The rest of the time, your Alternator does all of the powering of your vehicle. If your ALT is not big enough, then the battery tries to make up the difference until it goes dead.
Running 4 lights is not a problem, as long as your ALT is big enough to handle your vehicle's needs, plus the needs of the lights.
What wattage lights are you getting? Just for the sake of easy math, assume 10 watts of light needs 1 amp of power in a 12v automotive system. So if you get 4 lights, at 100 watts each, your looking at about 40 amps of power. You wont be wiring that up to your headlight wires thats for sure. Your looking at running a couple of 30amp relays from the battery, and some really nice #10 wire between the battery, the relays, and the lights. Dont forget a quality fuse holder with about 12" of the battery connection.
I just happened to make up a diagram for another guy this week, but it applies here also...