In my humble opinion.. any more than 3 gallons is a waste to me. I mean unless you are growing TREES. I think you could stick with 3 gal pots and grow all the bud you'll ever need and still have the room
I would switch to 3 gal bags, and give em a good shot of veg nutes and superthrive and just flip the lights to 12/12. This way you can keep the perpetual cycle in motion. Also sunleaves has grow bags of many sizes, and they offer a 1/2 gallon size that's killer for seedlings and clones to veg till ready for flower.
I go straight from the 1/2 gal or 1 gal bags to the 3 gals. The plants always have plenty of leg room and the harvests are of normal proportions... .8-1.0+ grams per watt
ANyways that's just my 2 cents mang