I know I'm late to this thread, but I do want to weigh in on the "10 week" time frame for growing an autoflower.
Now, I realize that the OP said that he had gotten it to flower by switching the lights to 12/12, so clearly the seed merchant sent photos not autos.
However, he also said that they were using synthetic nutrients, and were behind schedule.
So I'm growing my first plant, on the cusp of final harvest. A Northern Lights Auto, that formed its own proto-buds by week 4 with an 18/6 light cycle. It's a DWC, and I'm using
Advanced Nutrients products for nutrients. However, long story short, I wasn't aware of just how much the additive nutrient solutions changed the N-P-K ratios of the feed water. So my plant missed out on a lot of the Phosphorous and Potassium increase needed during flowering.
It grew to a giant, filling most of my tent, buds all over. But they were anemic in density because the buds never had the right nutritional supply.
So, here i sit at the end of week 14 (actual), and I have been in flush for 2 solid weeks, and this plant is STILL growing new fan leaves. I have no doubt at all by this point, that my plant would have gone 17 or more weeks had I not started the flush on week 12.
That was just before starting the flush, and 1 week prior to 1st harvest. And even though the pic says "W10-D6" that was week 12 (actual), since I had to readjust my time when I found all of those missing nutrients mid-grow.
The whole 10 weeks from seed to harvest angle promoted by the seed companies seems to be little more than a marketing tool. The lifespan of an autoflower will depend heavily on grow conditions, genetics, and other non-tangible factors.