You want to give your plant as long a day as possible while still maintaining flowering.
People that drop the hours of light during flowering haven't read Marijuana Botany, by Rob Clarke. He cites research that says that
"twice as much THC is produced under a 12-hour photoperiod than under a 10-hour photoperiod." (!!) Read that again...
Basically, light is what causes THC production and cannabinoid biosynthesis, so we want to give our plants as much light as we can, as long as it's less than the critical daylength of the strain, which is what keeps it in flowering.
From years of experience, we know that 12 hours of dark will keep them in flowering, so for best results you want to give them at least 12 hours of light, not less.
HTH