Flowering - When To Stop Pruning???

Today is the 3rd day of 12/12 for 17 Clones.

Their History.
31/12/13 - 24 Cuttings taken from 9 six week old Veg plants
(the next day they were put on 12/12).
The 24 Cuttings were put into rooting sponges
and into a propagator.
31/01/14 - 23 Established Cuttings potted into 6.5lts Hydroton.
18/6 MH light schedule - 13 Topped, 7 LST'd, 2 SuperCropped
01/03/14 - 17 Clones flipped to 12/12 light
(2 clones given an additional 8 hours of windowledge light -
to prevent flowering).

I have 17 Clones, covering a 4 x 4 floor space, under 600w HPS
At some point these 17 will need to be spread out
(I have 9 plants in a 4 x 4 tent so I know how crowded it will get).

In the next 3 week the 600w HPS will be accompanied with a 1000w HPS
and an area of 6 x 4 will be the available floor space.

AT WHAT STAGE OF FLOWER SHOULD I NO LONGER TRIM (OR PRUNE)
THESE PLANTS???

I like to have all my pruning done no later then day 14. Usually by day ten, if i'm not to busy. I don't touch shit up top in flower(except supercrop for canopy control). But i do prune/lollipop down low, if the setup calls for it. I like to get it done well before the end of the stretch.