I was born in a time when my mother was told smoking was good for my health.
They took it seriously: my parents ran a tobacconist and I grew up in and around a level of smoking that would make your eyes water. Literally, if you like.
So look at things you may think will last forever.
When your children are having grandchildren, some of the things you think will last are gone, and some of the things you think will never change, have changed.
Change is constant.