It depends on how often you usually dose the drug, as well as its half life. If someone has access to a lot of heroin and does some every 6 hours then they will soon find themselves getting six at the one hour mark, whereas a person using it once a day will usually make it closer to 24 hours before getting sick. With oxycodone the time seems shorter so even if you use just once a day it's usually only 12 hours or so before you start getting sick, but if you keep holding out until 24 hours before dosing you should start to not get sick for a little longer. Even when I was only using fri-sat-sun I would be fine until Thursday which is a long time to take to get sick but since my body became used to that dosing schedule it adjusted.
You are not going to find an exact amount of time but if you are taking it daily it's going to be between 6-22 hours generally. There's really only one way to find out, and that's through experience.
Edit: mr.scagnattie, great minds... and everything...