All you are doing is staggering when you move them from 18/6 to 12/12. Each strain for the most part has a pre-determined number of days of flowering and you can usually count on it give or take a day or 2. If all of you plants happen to be clones of 1 strain, say 10 purps, then you can count on the fact you will be harvesting in 60-65 days into flower. Now instead of 10, you only have 5 that you veg same # of days as usual(say 30, cut 5 clones a wk or 2 before you put them into flower. By the time you get roots, transition and veg for 30 days, than you are pretty much on time to harvest 5 at the same time you put the other 5 into flower. With more space you can get as short a time span as a few weeks in between harvesting plants but you are not shorting any one plant of any part of it's life cycle. Think of it as a car asembly line, versus taking 10 cars in a room and go circles till you have them all assembled. It's just streamlining but each car still has the same number of parts and took the same time to build. Another car is already prepped to replace one you just completed.