Sure can with no problems to worry about. The 18-6 schedule is what I use for veg along with most other people as well. Also FYI it's important that you allow your plants to sleep at least 4 hours. I say this because with every living thing requires some kind of rest and time to build necessary energy. Sure you can do 24 but IMO I find that I end up with a stronger and healthier plant when using 18-6. Hope this helps and good luck on your grow.
!! CHEERS!!!