I usually start chinenses in early January and others I start in mid February. This winter, I'm going to start later. If I can manage to hold off the itch to start playing in the dirt early, I'll plant chinenses in mid February and others in March.
Starting early is helpful because if seeds don't germ, there's time to start more. But lately, my plants have just been getting too damned big. When they outgrow their grow area, they get crowded. Crowded plants get spindly and weak. Weak, spindly plants are a pain in the ass to deal with. Later for that.