I recently started my first auto run, and of course I had to ask the very same question. 
I ended up settling on 24-hour light for the first few weeks, then switching over to 18/6 or so because that coincides with my veg room schedule and other plants needed rearranging. I’ll probably keep them on 18/6 since, as the thread suggests, there doesn’t turn out to be much difference other than the electric bill. Lots of people with experience and opinions, though, if you want to read up. 
OMG! A limited edition seed drop? That must mean they’re special, I must have them! Oh, wait, there’ll be another fifty limited editions of various new crosses by next week, and they should all be labeled “anonymous F2 polyhybrid with good parents and grandparents.” Step right up and get your ticket for the pheno hunt. 
Not that there’s anything wrong with pheno hunting, just tough to get excited over it or want to pay good money for the opportunity. I’d rather hunt through your Pentagram or other homemade polyhybrids instead.