I must admit, I've never intentionally done a 'proper' re-veg. I scrog and there is so little left under the screen after harvest, I doubt it would work.
What I have done, however, is have some vegging clones into flower when the better half's parents came to stay for a week. I had no choice but to put them in a mates grow room (unfortunately in 12/12) for the duration. It slowed me down a lot (maybe 3-4 weeks) but was interesting none the less.
On the other hand, this has got me thinking that after a harvest in mid-late summer, instead of binning the remaining plant, why not just plant it outside somewhere quiet? What's to lose?