Quite far in actually. Ive done it as late as a month and heard of others being successful even later. I personally like clones from flower as they tend to do some crazy branching when they revert back to veg. Pulling them when in the first 2 weeks of flower gives the best results. If there is a little budlet on top just tear off a little bit of it. If you do so it will aid in crazy branching.
big bud strain is very easy root. all i can say it all depend. i have 2 big bud clones i cut 6 weeks into flower on 3-8-09 one of them it took amonth to vert back to veg stage andnow she is in the flower room.she is about 4 ft tall now.the other is just now verting back.. it all depends.