Changing the Flower 12 to start later ?

Okay, So I'm thinking bout getting ready for the summer and am thinking that first off, off peak electricity is going to be cheaper, and second, running my flower room at night is going to present less of a heat problem.

Currently on time is about 10 am. I want to run these to start at 10 pm. Question is, having a full flower room, can I safely leave them in 24 hours of darknes or am I better off moving the 12 forard say in 15 minute bumps over the spring ?