You rig is ready for lifting when you no longer need your money for anything else
I started lifting mine when it was still under warranty. One of my [many] justifications was based on a question that I am often posed - "Why did you do that to a GC?". The answer is simply, because it's less likely to be damaged when 'froading. (of course that's BS because it just takes you to bigger and messier places, but it'll do).
My setup has cooper 33.1" tyres and they rub under full compression sometimes at the rear - I think only on the left. If I get the wheels re-centred under the body then it should go away because it is only just rubbing. I'm at a total of 5.25" lift, and if I had the original bumper it would never fit into that wheel well.