Time-wise and since it's the ultimate in simplicity to take as many cuttings as you like (well, within reason) before flowering, I've always felt that re-vegging was unnecessary. Some say that the quality can decrease. Most like to flush as many of the nutrients as possible out of the plant before harvesting. That would seem tough to do if your goal is to end up with a plant that is healthy enough to reveg. And you're still faced in the end with waiting for it to get over the switch to 24/0 stress, go back to 100% vegetative growth (which not every single strain will do - some end up continuing to "spit" flowers which makes for a plant that is not devoting all of its energy towards what you want it to), and then have your vegetative period.
But if you take a cutting before switching to flower, stick it in a glass of water on the window sill (ok, there are other ways and I'm actually a fan of Olivia's products but the oldskool way works a charm too) while it roots, and then stick it into your chosen medium, you've got a rooted plant that's already in the vegetative state the moment you're done flowering your existing crop. And it doesn't take much space or lights to keep a plant alive in a vegetative state if you're not trying to get it to actively grow. So you could stick it in a small box or a 30-gallon aluminum trash can with nothing more than a small amount of florescent lighting. You wouldn't even need to run it 24/0, 18/6, or whatever. Just set your timer so that the lights kick on regularly during the "lights-off" period so as to inhibit flowering. Keep the light as close to the plant as possible to prevent stretch, cut a few holes in the bottom of the can and a couple of slots in the bottom "lip" that holds the bottom of the can off the ground, add a very small fan for circulation, and you could stick it into the corner of your garage and nobody would notice it unless they tried to throw trash into the can (lol). At a time prior to your harvest date that you determine, you can then ramp up the lights and nutrients so that it will actually grow vegetatively instead of just... vegetating (you know what I mean?). Then when harvest time comes you can actually HARVEST 100% of the buds along with all of the trichome-coated leaves for the hash/etc. pot because you don't have to leave good product on the vine to revegetate. Then when you fight your way out of the scissors-hash-induced dreams the next morning you can stick your now well-grown vegetated plant into your flowering room (assuming that you've managed to grow it to the size that you require) and not even have to reset your light's timer.
IDK, I'm kind of medicated right now.
