Do You Use 18/6 or 24 hours of Light?

[Technique2]

I use 24/0 myself but downside would be extra expense on utilites, like was mentioned...

As well as shorter life span for ballast/lights and it takes a bit longer to show flowers when switching over to 12/12.

But does it stunt/slow growth of the plant in any way or show less vigor than say fluoros vs. MH/HPS?