Holy crap ! That's stupid slow. My G. aureostriata was less then an inch in Feb of this year. So far it has moulted 3 times, and is 2.25 inches. Not bad for 4 months !It all depends. I have a G. Rosea sling that I got last Sept, it was 3/4" when I got it. 9 months later its......................... 3/4" I have seen it eat, its nice and healthy. Just has chosen not to molt.
You should not have to wait anywhere near that long. No one can tell you for sure when its going to molt, but I dont think you will have to wait much longer.