Hello, I just checked on this board after some months, as it is still a comfort, even though my dad passed away rapidly about a year ago. I don't know where in the stream of things you are right now with your dad. I hope he is still holding his own.
You wondered when the time is nearing the end. There is no exact way of knowing, but when he is no longer eating and things are starting to shut down, it is very, very near. Don't hesitate to go see him, and do it now, rather than later...you never know how quickly things can go. I put off seeing my dad thinking we had a least a couple months more, and by the time I was ready to go see him, it was too late. I live about 12 hours away. I know he didn't want me to see him like he was, but I still wish I had been there to give him one last hug and kiss and tell him how much I loved him, before it was too late. I know he knew...but still.....
Don't hesitate.......just go. Everyone told me to go right away, but I think I was in denial a bit..............just go.
Thinking of you and your family,.