Our germinated seeds are planted in plastic drinking cups full of seed starter soil. Our clones are rooted in peat pucks covered in damp perlite in a covered pot on top of a heating pad. Both are moved to 3-liter bottles with their tops cut off full of our vegging soil mix when ready. This vegging soil always lasts until the plants are ready to flower. This includes topping them twice. Just before flowering, they get moved to either five or six gallon buckets full of our flowering mix and stay there 90 days until harvest.
Plants can grow extremely well in the right soil in the right conditions. Once you have a system the plants grow very well in, transplanting only interrupts the healthy growing process and usually should be kept to a minimum.