Hi Bamboo,
I solo'ed and then flew 1 hour, back in dual mode. Then, for one reason or another, I didn't fly for 7 weeks. Then last weekend we flew dual again BUT before we'd even set off, my instructor hinted at perhaps me going solo during this lesson.
However I thought it was more prudent to spend the hour in the circuit and just get used to it all again.
The Result, is that next lesson I'll be solo'ing again. So my answer to your question is 2 hours before I get my chance again.
My advice is, don't be too disheartend I was at the pre-solo stage when my previous instructor left for another job. I then flew 2 hours with my current instructor before I went solo.
Be patient, the more practice you get, the closer you'll be to perfection as regards circuit work.