time them to avoid the seasonal risks. can't really be too confident about advertised weeks to finish, so plan for the worst-case.
the variance of flower length is the same as a photoperiod. Autos vary further by an unknown amount of vege days. Unless you can send material into a lab, you can only guess when an autoflower actually went into flower. It's 7-8 days before you notice any preflowers, or however long it took for them to grow. Unless it's some XXL long-vege'ing autoflower variety, not going to see preflowers in vege phase, so it can be used to guesstimate actual flip to flower. When you take that into account, most stuff is 8-10 weeks just like a photoperiod. Building the same plant material, using the same inputs, making use of similar DLI... it can't skip steps.