Depends on how complicated the question is; sometimes they have to go back to an engineer. But that seems a bit excessive. I would email them again and mention you're still waiting. Couple times that happened to me, they actually issued me a credit for having to wait so long.

Well my question was relatively simple. I wasn't even going to ask but I decided to ask anyway just to be sure. I had contacted them on another issue couple of months ago and they replied in just couple of days. The agent was very polite and he did issue me a credit too. This new agent is not so good. The first time he replied to my first question he said I should use 320x100 ad for my header which I already did. Then I had another question and he said he will get back to me tomorrow (that's 8 days ago). I emailed him on Monday but no reply still.