i think this is the second most popular question of new growers...first being 'how much will I yield with...?', lol.
I promise, everyone will give you diff answers. basically, you need to decide what your goal is and do whatever you gotta do to reach it.
as there are many ways to grow indoors, there will be as many answers to your question!
I saw a guys grow, w/600w HPS, grew 45 plants, all under 2 feet tall....12/12 from seed.
but you could opt for growing only 2, 18/6 for 8wks, then another 8wks at 12/12...
IMO, you should set some goals for yourself, then ask the experts if it's feasible and how...