Alas, I don't have room for a 5x5, but do have the perfect tent for the space I do have, which ends up being 2.6'x5'x6.7' (33"x60"x80"). While lots of people here are focused on quantity harvest, I'm not. The tent works fine for 4ish smaller plants or as I'm doing right now, 2x plants I expect will get bigger. I don't go through any of it quick enough to need to prioritize high quantity.
I give about a week from the plant breaking the soil. I consider the first 'real' leaves to be the start of Veg. Then if I really need to think in weeks, my timeline remains consistent. Since seed-pushers estimates and schedules aren't accurate in the least, I don't really end up caring about the number of weeks in any particular capacity.