If you plan on winching frequently get a larger (higher output) alternator, and don't just "rev the engine periodically in between", either drive out (to assist the winch), or, bring the engine rpms up to around 2000 and hold them there.
A fully loaded winch is going to be drawing 3~400A, way more than your alternator will deliver at idle (or even at 2000 rpm), and that "additional" current requirement has to be met by the battery - winch long enough, and you'll flatten the battery, any battery - but, by increasing the alternator output, you're going to reduce the draw on the battery, and, by holding the rpms higher, even when not winching (for example, in between pulls), allows the battery to at least partially recharge.