Racing starts mid april around here unless you are the type who likes mud and ice. I suppose that would put around feb-march to be the main part of build.
Ill start to push longer intervals, I race track all winter so Z7/6 is covered weekly as it is. I need to start pushing Z4 again as I can't do it on the trainer or the track, so that will be mainly what feb/march will be for me. Some longer Z3 rides in the sun would be nice. Some day...