I agree with everyone else. We are all different.
For me, using up to 120-140 mg of oxycodone/opana daily, my psychological cravings last for a few weeks. However, if I wean down with help from Methadone, at low doses, my physical cravings last about a week.
It's hard for me to go cold turkey, as I can't take the leg cramps, especially with my job.
So in all, I'd say a good 2-3 weeks for the body and mind to stop craving.