Yeah, the older guys still have plenty of jumping power whenever they want up somewhere! My last two fosters, Bob and Bess (who were 7), could easily make it onto the bed and the couch (despite my best efforts at keeping them otherwise :>) but both had problems in the cage going up to levels. I think the more enclosed space was just a bit more awkward, and that bigger, open jumps didn't give them quite so much trouble. I eventually removed all their shelves and just gave them a giant 2x5 with a flat floorplan.
We are as gods to the beasts of the fields. We order the time o' their birth and the time o' their death. Between times, we ha' a duty. - Terry Pratchett.
"Men have forgotten this truth", said the fox, "But you must not forget it. You become responsible, forever, for what you have tamed. - Antoine de Saint-Exupéry