They're are many arguments for and against 24/0. I personally use 18/6 and every single plant i have grown under 18/6 has grown faster than under 24/0.

The plant gathers energy in the dark cycle for photosynthesis, so this is why 18/6 is normally prefered, although clones do better under 24/0 for the first week or so.

And, no, the extra darkness wont affect the plant too much, but make sure it doesnt happen to often.

The plant measures the time of un-interuppted darkness which realses a flowering hormone, so if you keep having the lights off your plant will flower.