I watched a Stallone documentary the other day and unfortunately he had one very real quote that hit me hard, especially as I've just turned 40.
"Life is addition up until 40, then it's about subtraction".
Sad but true and you have to mentally prepare yourself to accept it. While you're viewing it as your parents, its everyone sadly. Most of your friends will eventually pass or you'll be the one to go. Children grow up and leave the nest. People retire and lose their social connections at work. Parents are very important and I'm extremely thankful both of mine still alive (almost 79 and going on 70), but the point is that deaths or loss of connections is something we have to cope with as we age.
Make the most of the time you have as it's a finite clock. Take some vacations or research some "things to ask your parents" lists, there's a ton out there. I see my parents about an hour or so every week and typically the conversation is surface level "how's it going / what's new / so and so did this / etc.", but when you get actively plan some deeper stuff, you really learn. This past Xmas season I asked really pointed questions about their childhood Xmas memories and learned some things I never knew before. Just take things a bit deeper when you can and accept the fact that time catches up to us all.