You should do the long miles if you can. Like ferret says, 10-16 hours/week of it with long rides. That's great if you live somewhere that you can do it. But cutting back on intensity if you can't do big miles doesn't work at all. If you're doing base, you want to be in almost the same state of general tiredness you were in during the summer, but doing more hours and mileage than you were doing. IME "resting" won't give you gains the next season. Quite the contrary. Long miles will. This isn't slow riding either, just keeping the effort down, mostly below the level of leg pain. Mostly zone 2 like a double century effort.

I can't do the long miles in winter, so I mix it up: roller drills and Z3 intervals, skiing and snowshoeing, weights, spin class, and one longish, hardish ride/week. So I'm still getting ~10 hours/week on a good week, though more time and miles would certainly be better. The good thing about mixing it up is injury prevention: making sure that there's muscle balance and flexibility throughout the body.