how often do you want a harvest? work backward from there relative to the typical amount of time it takes for a full grow and dry/cure. that will determine the gap you need before starting next round of plants.
because plants will be at varying stages, you can have a greater number in same sized area than normal. whether your size is sufficient enough for your need is another calculation.
if you want a harvest every 2 weeks you need to starta new round of plants every 2 weeks. if it takes you 14 weeks to vege and bloom, then you'll have 7 'rounds' of plants at varying stages of development. 1 plant? 2 plants? can you fit 14 in to teh area? some will be quite small or even in a seedling area etc etc.. so more than normal is possible, but also risky to become a giant mess if not workign with clones with same exact development rate as each other. somem plants will take 16 weeks, others may take 13. it'll be nearly impossible to keep it smoothly running, i know from experience. you'll be more productive (a rate*) doing full runs and overlapping a bit - how long before a seedling needs to be under the big lights? the overlap can be 2-3 weeks or more in some cases, which will easily allow 5 harvests per year instead of 4. that's 125% more productive per year give or take. perpetual grow will never be efficient due to the incongruent development rates of the plants grown. always a mess, always gaps left open or overgrown to make up differences experienced over time etc etc... a mess.