You have to be present in order to improve. That gets harder the longer you study one thing because you must continue to stay interested, finding new ways to improve and develop.
I've been absolutely floored - mentally, not physically! - from time to time (not often, but just often enough that it's left real impressions on me) when visiting a dojo or off at a seminar, and having someone clearly of high rank w/ many years in the art partner with me and give the most ho-hum, unconnected attack, literally looking somewhere else and acting as if ready to start a conversation w/ somebody over there, w/ no attempt at connection. And I wonder why they bother showing up at all.