depends on the dosage and how often you take them. For example, I don't know anyone who has lasted longer than 6 weeks at 50mg/ed. But there are some people who keep the dosage low and skip weekends. I've heard of cycles running as long as a few months without a major effect on liver values.
Me personally, if I go over 40mg's for longer than 3 weeks straight, I turn into a hunched over old man.
ive never gone over 5 wks however ive hered of people going for months i think if your drinking your water every day you should be fine for up to 6 or 7 wks
I've gone 50 mgs/day for 8 weeks with no problems. This is nothing compared to what the old timers used to do. They'd stay on for months at a time. The danger of orals is vastly exaggerated. You need to use your head and be cautious as with anything else. I know guys that have gone for 3 months w/o problems too.