I have a vast amount of experience with a variety of synthetic and natural fiber lines having spent the first 20 years of my adult life in the Navy on ships. A couple of suggestions for anyone here wanting to have some sort of fairlead sleeve or something to protect the line from chafing:
1. Visit your local fire department and ask if they have any small diameter fire hose that has aged out of service. You only need a couple feet. You cut it long ways and will have to sew it using a very large sail needle and a twine or, better yet, paracord.
2. Use a piece from an old canvas drop cloth, if you have one, to accomplish the same trick.
3. An old garden hose also works, depending on the diameter of the line you're working with. If not, go to your nearest home improvement store where they sell tubing by the foot and find something you think will work.
Couple thoughts on the care and maintenance of winch line:
1. Both natural fiber and synthetic line, if exposed to the elements, are prone to mold. At least once a year during the heat of the day, unspool the line and lay it our on the driveway so any moisture can evaporate.
2. Because the line spools on and off in the same direction, the line can begin to "unlay." Unspool the line occasionally and let it relax laid out on the driveway. Kind of like the garden house when it gets twisted from being coiled the same direction every time it's used.
Synthetic line, although it is relatively inexpensive, easy to work with and is clearly the choice of most off-road winch users, is also the most dangerous. Most of the mooring lines we used in the Navy on combatants were 6" and some 8" diameter nylon lines. When put under extreme tension, a 6" line can reduce itself to less than 2" in diameter before it snaps. And, when it does, it will destroy almost anything it hits when it recoils. Just think of a giant rubber band.
Natural fiber line, on the other hand, does not have the same elasticity, but will still do damage when it parts. You may have to do a trail repair just to have something on the remainder of your trip, but under no circumstances should you continue to use a winch line that has been stretched to near maximum or to a point where it actually parted.