The Cervantes book says that you have to flower when the plant is done with its seedling stage after several weeks. Its interesting how, on the net, you find people doing things that they're 'not supposed to' do.
I don't have a copy, but I strongly doubt that Jorge Cervantes said you "have" to flower when the plant is done with its seedling stage after several weeks.
In fact, many (if not most) growers do NOT do that, and I'm 100% sure Cervantes knows this. Instead of flowering immediately after a few weeks of seedling stage, when the plant becomes sexually mature, many growers will then let their plant continue to grow in vegetative stage while training it (or not), until it reaches a desired size and or configuration. At that point, once its the size/shape they like, THEN they'll force it to flower.
So I'd imagine what Cervantes probably said is that after only a few weeks you COULD make the plant flower (not you "have" to!).
In terms of the premise of the original question, yield is HIGHLY strain dependent. That makes it a bit unfair to generalize comparisons between autoflowers vs regular strains without specifying which exact strains you're comparing.
The biggest yield advantage of something like an autoflower is that during flowering, instead of running the lights 12on/12off you're running them 20on/4off (or even 24 on).
So in, say the 4-5 week period where the autoflower is flowering, its receiving the same amount of total light as a photoperiod plant would receive during a full 8 weeks of flowering.
That's why autoflowers fill out so much in relatively few calendar days, and why you can get a respectable yield with what amounts to only a month of real flowering.
I think FROM SEED, all else being equal, the ability to run lights longer would give autoflowers a yield advantage in a given number of calendar days compared to normal/photoperiod plants. But I think its also fair to point out that seriously interested in maximizing yield per square foot usually aren't growing from seed. . .they're growing from clones.
If you compare a rooted clone at 12-12 (or even 14-10) vs an autoflower from seed, the comparison becomes a lot more interesting. I won't rehash my whole argument here, but I'll excerpt it briefly from the 7th post in this "autoflower" thread:
https://www.rollitup.org/auto-flowering-strains/493268-if-any-strain-can-crossed.html
I'm also not entirely convinced that autos are more space efficient than classical sea of green gardening using large numbers of rooted clones.
In general, autos don't like transplanting, and from germinated seeds, you still need at least 3 weeks of seedling type growth before they start to flower. Unless you're using feminized auto seeds, you'll then have to cull out males, meaning you'd have to start with potentially twice the number of seeds as plants you'd ultimately want to keep. Meanwhile, rooted photoperiod clones (which can be started in a relatively small space and are amenable to transplant) will start flowering literally as soon as you plant them into 12-12, and you can do this with ANY photoperiod strain you like.
Assuming you planted the two side by side, by the time your female autoflowers have just started to flower under 24-0 lighting, the 12-12 photoperiod clones have already been flowering for three full weeks. At that rate, it would take until week six before the clones and autoflowers have received the same number of hours of light during active flowering time. If harvest were at week 7 or 8, the autos only get the added benefit of 24 hour lighting for another 1-2 weeks over the conventional photoperiod clones before harvest. That's not all that much of an advantage, and you have to weight it against the need to acquire and start from seeds, cull males, etc.
Meanwhile, some people believe that dark time is necessary for plants to achieve max potency. If you believe this, you might want to flower your autos under 20-4. Conversely you might want to flower your photoperiod clones under 14-10 for max bud production. Under that comparison, the autos and clones don't achieve flowering light parity until the end of week 8. . .now you're already at harvest time. If your autos don't flower until week 4, you're at harvest before they "catch up" to the clones.
If you run your autos at 18-6, they also probably won't quite "catch up" to rooted clones in a reasonable 8 week harvest cycle.
