another lighting question

I only leave my lights on 12 hours I was told I should leave them on 24. Any suggestions?

It depends on whether or not you are flowering or in the veg cycle. Generally speaking people use the system of 12 hours on 12 hours off for flowering and for veg most people use 18 on 6 off but some do use 24 on 0 off.

I'm in the veg cycle

Ok then what most people would say is the best is to keep your lights on 18 hours and 6 hours off.

18+ hours...
cheers