How long con you keep growing?

I have a plant that grew some beautiful bud. About 3 weeks ago I got a new set of growth. I trimmed all the lower nugs right up to about 4-6" from the tops. I am using 1000 watt MH @ 12/12 How long can I keep growing?

That current plant will grow until the Tricomes (resin glands) start dieing (over ripe) then the plant itself will quit taking in nutes/water/etc and fade away.

if you have new growth, put it back in veg till it gets where ya want it then flip it to flower and go again