As a sniffer...I'm usually fine in 72 hours(physically) after last use of heroin. Estimate binge to be, oh, 50 days on average till I'm forced to WD.
Oxycontin, on a similar binge? Takes around 100+ hours, I find the kicking/insomnia MUCH worse.
Those were my experiences before I did some research on how to tame WD's...nowadays...
With that being said, when I tell myself that WD's really aren't that bad compared to many things, my mind does play some tricks that help me out. It is mind over matter most of the time, if you're able to channel that real, but hard to understand phenomenon. It doesn't make any logical sense, but it works like a charm. If I'm thinking, oh shit, this is going to be friggin terrible, it certainly is...without exception. If I tell myself, yeah..this is kind of like having the flu, I'll be good in a few days... for the most part now, the physical WD's can be kept in relative check...still apparent, and kicking may come into play around the 2am-4am mark on night two of WD, but I'm all good from a physical stand point after 48 hours.
The mental cravings, on the other, can't be kept in check by "out-thinking" your own brain. The pull of the drug will ALWAYS be there in opiate addicts...ALWAYS, imo. Over time it may diminish, but it will lurk in the back of one's head till the day he or she dies.