Waiting time for Gardisil?

I received 2 gardisil shots. My third one is due in a month or so but I can't find it. I'm originally from Canada so I got the 2 shots because they be free. I moved to the US and forgot that I had to attain one more. I want to hang about a few extra months to get the finishing shot because I'll be covered by insurance but I wanted to know if the shot will even work after so long. Does anyone know? the third shot is in recent times a booster shot. i dont think i will affect it any.
Check beside the CDC. Sometimes time frames between boosters is VERY important.