I have read somewhere that it usually takes at least two weeks of around the clock dosing on opiates to become dependent. That's why most people who have surgery and take opiates for a week don't need to be weaned off.
However, everyone is different. I also think if a person was a prior opiate addict then they might become dependent sooner. Although, that's just speculation on my part. Certainly they would be more at risk for psychological dependance (aka: addiction). If you're worried then I would talk to your doctor hon. But, IMO, I think you'll be fine.