I do about a half how before and after with my actinics. You definitely are doing it right and should keep them on all day. They are providing a different wavelength for whatever you have living in your tank. As far as it making a sunrise sunset scenario, there is no benefit for animals within your tank, it is just pleasing to our eyes. So it is not necessary, but I do it anyway. I like seeing some of my corals that glow under just actinics for a little while at night.