Long after he could no longer cast a spinning rod my dad retained the old muscle memory to throw a fly rod. In his late nineties he couldn't take more than about 3-4 hours on the river, but he caught a couple of good ones still.

Fishing might have been the last coffin nail for him; at 99 I took him to a high altitude lake to row him around in my drift boat and troll. Our long drought had left all the other boat ramps hanging high and dry, but we had a good afternoon catching small trout. The next day he started falling, having delusions, I suspect the thin oxygen was just too much, All the symptoms increased until three months later, one month short of 100, he died of heart failure.

So sorry to hear that your dad is leaving you. People tell me that I was a "good son", and sometimes that rings hollow, given the struggles and feelings I had during his long decline. Take it from one who has been there, you're doing a good job and demonstrating that he raised a good son;)