How long is end of life?

My dad has stage 4 Colon cancer which has metatasised to his liver. He also has cancer in his prostate and they think a bit in his lung too.

He was advised to stop treatment back in August.

He is 79 and wont be honest to us about he's feeling.

How long is he likely to have left?

My mum has demetia so trying to put in plans.