"Dragons live forever, but not so little kittens …"
At 13 1/2 years old, Penwiper is still a reasonably limber jumper & climber. But he's no longer quite in the prime of life.
Last week I heard a scrambling noise that sounded like he had missed a jump onto the upstairs hall railing. This is something that he had consistently made for years.
In the past few weeks, I also noticed that he gets onto the kitchen counter for kitty treats differently. Rather than him doing a direct jump from the floor to the counter, he takes the scenic route via the wastebasket at the end of counter as an intermediate step. This is not a terrible thing, but it does say that he's not feeling like two-year-old catten anymore.