Thank-you all for your comments! I think "galaxy season" or "spring galaxies" comes from visual astronomy and predates astrophotography. April is a great time to view galaxies from RA 10 hrs to 14 hrs in the early evening. OTOH, the galaxies around 10 hrs reach the meridian in early December at the beginning of morning twilight and can be photographed now.
Clear skies and excellent seeing to all you galaxy astrophotographers!
I've been imaging galaxies now as well. I have another 25-30 hours to go on M81 and will move to M101 next. Sure, visually, it makes sense for spring to be galaxy season. In early winter though I can start imaging M81 around 9 pm at roughly 35 degrees in apparent and between filter changes, focusing, and a meridian flip, get about 6-7 hours on target before dawn start creeping in. Forcing my hand is that I do have an obstructing tree that everyone seems to love and is among the healthiest trees I have ever seen after surviving a beetle infestation. In the spring, that tree becomes problematic.
George