[BKKG]

You're not going to make up much in width or height if you switch your plants to 12/12, regardless of where the lights are located, because that light cycle causes the plants to put more energy into bud production rather than growth that will produce new bud sites. However, more lights will help the harvest overall. Anyways, you can switch to 12/12 whenever you want, but if the plant isn't mature enough it won't start to flower (generally the veg stage takes about a month, although that varies some from plant to plant).

By the time you lease is up, your plants may or may not be ready to harvest, the only way to know when they're ready is to look at the color of the trichs, no one can predict exactly when they'll be ready for you.

You don't have to worry too much about your new grow space not being 100% like your old one, you just have to make sure that the plants are getting enough light, fresh air, etc. A move without transplanting to new soil probably wouldn't stress them too badly, unless you expose them to light during their dark period. I'd recommend moving them during their light cycle, as that way it won't matter if they're exposed to light or not.

You could also just chop the plants as close to your move-out date as possible, but again, it may be a bit early for them and you'd give up some quality for it.