A friend's husband was in a crash a month ago and was ejected from the vehicle during the rollover. He's paralyzed and cannot breathe on his own.

How long can a person be kept in a medically induced coma?

The guy has been living apart from my friend but not legally separated. He's a steaming pile of shit and nobody who likes her thought she did the right thing in marrying him. Personally I hope she pulls the plug on him, but if she and the doctors can't ethically justify ending him I'm wondering if the meds will do it for them. The guy is a drunken, drugged up, violent, lying manipulator. His whole family is trash and I'm not sure he's even suitable as fertilizer. He crashed because he ran into someone even more violent and they ran his car off the road in the middle of nowhere, in the middle of the night, and left him to die. Arrests have been made, hopefully just for littering....

For an absurdly long time...think years, think normal life span in some cases....
We have progressed to a point where people have to be removed from ventilators. but they could live on them for a very long period of time.
The question in most cases isn't how long can the person live on the vent, it is when is the right time to take them off of the vent.
Quality of life goes to complete shit...but people can live a long time on a vent.

Shitty situation.

I was in an induced coma for almost three weeks, year before last.

The biggest problem I had directly related to the prolonged sedation was muscle atrophy. When I left the hospital I could barely sit up on my own, much less stand and certainly not walk, it took about three months of therapy to get to the point where I could walk normally (relatively) again.

From your description, this would matter little since he would be paralyzed anyway.

So the medicine doesn't harm the liver over time, or build toxicity?

It probably would, but they can treat that too. Cases like this are why my wife knows my wishes-no machines. Not because I don't believe in life support, but because I don't want someone else to have to make the decision of when to turn those machines off.If they are never turned on the question doesn't arise.

Several election cycles:

So have you proposed to her yet?

In before Arfcom goes all "Terry Schiavo!!!" on OP.

Given a feeding tube and a vent, a person can be kept going for years. They will eventually die of pneumonia or infection/bedsores, but those can be kept at bay for a while.

Well done!

I'm no expert in these matters but I've seen similar stuff play out.

She may want to speak to a financial advisor and/or lawyer about sequestering assets away in a manner that would preclude them from being seized for his care.  This might start with a divorce but I'm not sure.

One thing I do know, she's in a fucking minefield right now and had better be damned careful in how she tries to get out.

They are temporary. The doctors will be looking to pull him out of it before too much more time elapses.

eta: sorry, didn't answer the thread title's question. I don't know how long the average person can last before serious morbidity/mortality issues start to arise. but the longest I've heard of someone being kept in a MIC was close to half a year.