Ending 12/12 Outdoors ???????

The plants are in pots, in the garden, they are X-Line Sour Northern Lights X Nevilles' Haze. Germed end of March, vegged for 2 months, then 12/12 for the past month. The blurb reckons a flowering period of 10/12 weeks (though opinions seem to vary from 7-16 weeks) and mine are budding up nicely. Unfortunetly security is not 100% and the times when I am most vunerable to prying eyes are those when I am either putting them away each p.m or getting 'em out in the a.m. I'm also getting a hernia from struggling to carefully get a 4 foot wide plant through a 28 inch shed doorway, I don't want to snap anything or leave a bunch of lovely THC ladened trichomes stuck to the door frame. I know that plants revert to vegging if they are taken off 12/12, but surely there must come a point where the plant is so far into flowering that even though light hours increase it won't revert. So my question is when can I stop putting them away without screwing up the flowering process? Logic tells me that, say, the last week before harvest would surely be fine, but the last 2 weeks? Month? Who knows? I am at 50 N latitude.

Build yourself a hoop house and buy a big roll of black plastic.
Instead of moving the plants, simply toss the plastic up over the frame.
Personally I would not mess with light time. Last week maybe... but before that, they might start throwing nanners, with enough time to give you some unripe seeds.