First, no alternator can keep up with a fully loaded winch which can draw over 400 amps. That said, it is rare for a winch to be maxed out (fully loaded), most winch pulls are for substantially less than their rating and usually for short periods of time. I do quite a bit of winching & most winch pulls are on-off-on for 30 seconds or so. Rare is the long fully loaded pull.
That said, I wouldn't hesitate using the winch at night with driving lights on with my single Diehard Platinum battery with the factory 117 amp alternator for a typical pull. And proper battery management says if you're doing a long pull, break it into a few shorter pulls and give it a rest so the winch can cool off and the alternator can catch up with the battery's charge.
In 16 years of winching with two Warns on two different TJs, some of which were some pretty tough pulls, I've never drained my single battery. In fact, I've had to winch my TJ off the trail twice on pure battery power alone when I couldn't start the engine. Both times I was able to start the engine after fixing the problem and never needed a jump start.
If I had ever been given actual reason to install dual batteries, I'd have done so many years ago. I know that none of the even harder-core wheeling buddies I enjoy wheeling with ever bothered with dual batteries.
Dual batteries are usually a solution in search of a problem that is usually installed by those who have more $$$ than actual trail experience.