I'd say 6 hours max to hold you over, more like 3 or 4. I'm surprised 50mg oxy even held you over, you must have a low tolerance / get pretty standard, shitty smack as I wouldn't even feel that dose really during my days of heroin abuse and I was sniffing around the same dose as you per day (but the highest quality and therefore most expensive stuff around, really... worst life decision ever).
I recommend quitting if you have been regularly using for a month as it can and will become much worse over time... withdrawal gets worse and worse as the habit progresses and becomes a long term, multi-year thing. Just some friendly advice, if it has only been a month of regular use your withdrawal symptoms will become MUCH worse say, a year or two from now until perhaps rehab, jail, suboxone, or death are the only real options. I'm not sure if you feel like you are burning alive on the stake or not yet... withdrawal is subjective like that, but that's what it felt like for me this past summer. I wouldn't have been able to open my computer and type in withdrawal. I would become downright morbidly suicidal for at least a week, and be unable to so much as get out of bed in time to make it to the washroom. I would have slit my wrists to escape it if I had the strength and willpower, but my spirit had been leached of the will to do anything at all whatsoever, and my brain had been hijacked by extreme, unbearable, relentless suffering. I was unable to hold food down, or even water and I was shitting my pants constantly, even with loperamide. My entire body felt like it was ablaze in the depths of hell... get out while you still can (I say this in the friendliest way and respect your life choices of course... but this is a dumbass fuckin decision you are making).
I mean this in the friendliest way possible as I have been there myself (5 years of daily use) - but what, exactly, the fuck are you doing with your life? Got a plan for the future other than progressing the worst addiction on the planet until you statistically end up dead? Just thinking about how it ended with heroin can not only bring me to tears, but trigger lingering withdrawal symptoms that set every nerve in my spine aflame with extreme, unbearable agony.