When it comes to the time I have to replace my 2 50/50's on my 130watt PC. I'll be doing 1 10k and 1 Act. I'll be able to have a better day to night then anyway.
I have 4 rows of fluoros', with 3 actinic and 1 10k. One of my actinic rows acts as the dawn and dusk light and is set to turn on before the others in the morning, and after the others in the evening. Works fine for me