I took clones off of my White Russians about 4 weeks in.
I wanted to do it earlier but the circumstances wouldn't allow it.
The clones take about the same amount of time to 'root out', as they would if you took them during veg. However, they take much longer to start actually growing. Mine seemed to take a few weeks to a month!
One benefit though. When the plants did start growing again they shot out multiple tops. I didn't have to top anything and my plants had 4-6 tops.
Thought that was pretty cool. and may actually do some late cloning again this time around.