Firefish are funny little creatures. I've had mine for about 4 mos now, and for the better part of those four months he slowly overcame his shyness and was out and about all day with a clown and a damsel. This weekend I introduced a flame angel and now he's back in hiding again. I've watched him closely when he does venture out, and he seems to hate being "snuck up on" from behind by the angel. This usually leads to him going into hiding for an hour. I'm considering closing off the angels access to the tunnel that allows him to sneak up on the firefish w/ a piece of live rock. I'm a little hesitant that this will impair water circulation, but I do want the firefish to feel comfortable.
In your case, I would just continue to wait unless you can identify something in the tank that is making him ill at ease. Let me know if you figure something out.