why is it taking this long
Blanketing is a good idea, absolutelyI'm not sure where you live, but generally, if your horse isn't clipped and is healthy enough to have grown a full winter coat, a sheet to keep him dry and protected from the elements is probably plenty.
I think it's fine if the horse needs it, but you do have to watch temperatures to make sure your horse doesn't get too hot/coldWhen you put a sheet on a horse, it lays the hair down, which can actually make the horse colder if the blanket doesn't have insulation.
I live in Vancouver and it gets pretty cold here so I always have a blanket on my horse in winterIt really does keep them warm and it's so much easier to groom them when their clean from the blanketI would definitely suggest getting a turnout blanket for your horse.
If it's already gotten cold where you live (and I assume it has) and you haven't been blanketing him, I wouldn't startHe would have already adapted to the cold and grown a winter coat, which is insulatingIf you put something on top of it, you limit the hair's natural ability to keep him warmSo in other words, you would have to blanket even more to compensate, instead of just throwing a sheet or lightweight blanket on over his winter coatIf he hasn't grown a winter coat yet and/or if you body clip him, then yes, blanket him (since he doesn't have the natural insulation)In the future, if you ever want to keep his coat short and shiny during the winter, start blanketing at the first sign of cold weather, before he has a chance to grow a winter coatMy family blankets two of our horses (the two that show throughout the winter) and not the other two (who stay outside and get furry).
There could be a coverage issueHe should have filed it under his OWN insuranceIt's highly possible that now, two years later, it's too late to claim under someone else's.
