I don't know how fast your growroom loses heat...so you are going to have to experiment with your setup.
My lights go off at 0830 and come on at 2030 in flower because I have less control over temps than I'd like... but the seedlings and veg are on 24h and I don't worry about m/f ratios, just survival, lol!
Ask again in winter... I may just say to hell with it and move back into the cellar growroom that holds heat better, and tell my tenant to just suck it up and deal!