How long can you live doing nothing all day long?

I have an aunt who is retired and just lays on her lounge chair all day. She’s 68 years old. 5’10 and about 340 pounds. She can barely walk. If she has to go down the stairs, she goes down on her butt. She eats the worst foods imaginable and has her groceries delivered and orders out a lot. She barely ever leaves the house. How long can someone live like this?