“A person can remain asymptomatic for years, although 5–7% of those with the condition will develop symptoms every year. Decompensated cirrhosis: People with decompensated cirrhosis already experience symptoms and complications.”
https://www.medicalnewstoday.com/articles/cirrhosis-of-the-liver-life-expectancy#life-expectancy-by-stage
Could be many years.
I’ve had ESLD since January 2008
Depends more on MELD or CHILD/PUGH score how severe the liver disease is. Is the Pearson symptomatic? Do they have Ascities requiring draining? Do they have bleeding esophageal varicies? Do the have Hepatic encepatholopathy? All those combined could be an indication the person has very advanced liver disease and is in liver failure.
If the person is able to prevent additional liver damage like curing hepatitis C or stopping all drinking the liver may actually have a chance to improve with time. Or at least not continue to decline. If that happens it is possible the person could live long enough to pass away from something other than liver disease.
The best person to ask would be the persons liver specialist.
Also if the patient gets to the point they need and qualify for a liver transplant they could live a full life span.