When should I move my crested gecko to a larger tank?

I am ordering the new sri lanka exo terra 18x18x24. He is about 3-4 inches long. He doesn't seem happy in his 10g anymore so thats why I'm ordering the new one. He is 5.5 months old. Is it a good time to move him? He is fed on a pangea mushroom ledge and has a small plate of food on his rock that he likes to sit on. Should he be able to find his food easily?