I used to be a year-round rider - if there wasn't snow or ice on the roads, I was game, no matter how cold. These days, I find I seldom get the bike out over the winter and, sure enough, come springtime, my reflexes and instincts are dull as dishwater. It takes a few rides to blow the cobwebs out, so I'm extra cautious and observant for those first few hours back on the bike.
Then, since everyone else on the road is either an inattentive knobhead or actively trying to murder me, I try to maintain that level of vigilance for the rest of the riding season.