I've tried taking clones later into flowering and I found that 2 weeks seemed to be the cutoff for it to work best. First thing I noticed was a decrease in percentage of successful rooting, but the later they were taken, the more my clones would do weird stuff. Like root, sit there and do nothing, or root and continue to grow, but not vegetatively. 4, 5 + weeks in, if they rooted, they'd very slowly try to grow buds in the cloner, but in a super weird way that didn't even look like weed. If they didn't die doing that, they had to be under 18/6 for another month to go back to veg growth. So the clones taken too late wouldn't be able to get going in time to be swapped back in to the cycle. (staged harvest every 2 weeks)