That's just it. It's really rare to find a 25 year old with a stagnant set of skills. I don't know if stagnation is the best word, but I also think there are other elements. Complacency in some cases, or getting too comfortable.
Most of the successful tech people I know that are 50+ never overstayed their welcome at companies where they stopped learning, or they were always being recruited by other firms and moved around. Recruiters generally aren't knocking on doors of someone who has been at the same company for 20 years, and that's for a variety of reasons.