How long after plant stops getting taller until harvest?

I've been growing for a year or so using autos under a 300w (true wattage) dual spectrum CFL. Recently I was sent a few freebie seeds but after planting realised these were true cannabis strains, not automatics.

Anyway, all is going well, I changed to 12/12 about three weeks in and the plant is now budding nicely. My question is, at why point in the life cycle does the vertical growth finally stop? It was gaining an inch every few days until this weekend and now seems to have stopped completely. From this, approximately how long do you think is left until harvest? I know each plant is different so I'm only after a very rough estimate.

Excuse the spelling/grammar, posting on iPhone.

That's right, about 2-3 weeks into 12/12 vertical growth comes to a near-stop and then you're looking at anywhere from 6-12 weeks to harvest from there, closer to 6 for indica-dominant strains and as much as 12 on sativas.

It's possible for them to double in size after being put into flower or even more, but generally I plan my grows to put into flower at half the max height I can tolerate.