I think the general rule is that this is the time to put in the hours, but not really the effort. I'm a total weekend warrior, sub 3k miles a year, kind of guy. Last winter, my goal was 60 hours before really ramping up to hard intervals. I had my best season ever with that plan. Some people will hit that in a few weeks, and others will take an entire season to hit it, but it was a good goal for me, given my work and family schedule. Most of that time was on the trainer, an hour or so at a time, but when I got outside on weekends, I loved just lumbering along with no worry about pace or effort. Once I increased the effort in February or so, I felt great, and with some HIIT in March and April, I crushed my spring 100k PR. By the summer, I was starting to burn out a bit, but I still was fit, and managed to top my 20k TT PR.

It is all about your overall goals, but this is the time of year that I enjoy doing easy trainer rides watching Netflix or ambling about on the weekends without a care.