the roots naturally go out to the edge of the container then down to the bottom, leaving the middle relatively unused. the more times you transplant the better of a root ball you get. if you let the plant fill each consecutive container with roots, then by the time you do the final transplant to 5 gal bucket the roots will pretty much fil the entire container from the center all the way to the edges. more roots = more buds!!!! also if you start a plant in a large pot it will take a very long time to dry out. imo it is best if the container dries out in 2-3 days no matter what size the plant/pot. if it takes a week or more to dry that means you can only fertilize that often, unless you foliar feed but i wouldn't suggest trying that with a budding plant. as long as you are very careful while transplanting there is no reason you should stress the plant or even see slowed growth. i have noticed quite the opsite myself. after a transplant the plant seems to have a nice growth spurt in the 1st 1-3 days! i always used thrive alive B1 (green)when transplanting as well. imo the more times you can transplant the better your yeilds will be! people say it slows the growth, i don't think so but even if it does slow it a few days who cares, the final product is worth it. also if you are in a hurry growing cannabis is not the hobby for you. hope this helps