Hi, Drugstore, and welcome to the forum! Is your hepatitis C chronic active? If so, no, you won't just suddenly die. I have hep C, diagnosed in '93, and cirrhosis. I tried interferon treatment (the only thing available back then) and developed very low white counts, so was taken off treatment. It didn't seem to be working for me, anyway. So I coasted along, doing nothing treatment-wise, but had stopped drinking 6 years prior to diagnosis (and stopped using drugs long before that.) So I was a little surprised (and a lot afraid) to learn in '95 that I had liver cancer. Thanks to Mayo Jacksonville, I'm still here, minus most of my liver.
Is there a reason you haven't tried treatment for hep C? I don't know if you could remain on methadone if you were on treatment. Do you know if methadone is harmful to your liver? I assume you are using it to stay clean. (I kicked H cold turkey in '69 and have never gone back.)
What aggravates hep C? Alcohol is #1. Drugs that are harmful to the liver. Lack of rest. Poor diet (try to eat fresh fruits and veggies and avoid beef.) Stress. I'm impressed that you are able to work full time. I found the fatigue so overwhelming that I could only work P/T from '93 until 2005, when I got SSD approval.
I can tell you that without treatment, you will eventually probably develop cirrhosis or liver cancer or both. It does take time for this to happen, but if you can possibly get treatment and it works for you--then you will avoid a premature death.
Oldfriend, methadone might be a good pain med for your dad. Speak to his doctor about it. Of course, he can't take that AND opium!