The success rate for all types of coaches is low.
With elite schools where the funding, desire, and tradition are there to compete (Ohio State, Alabama, etc.), the hit rate is higher because they are fishing for known commodities. It was not a risk to hire Nick Saban at Alabama or Urban Meyer at Ohio State. And when they do make a mistake, the problem gets resolved quickly.
I don’t think there is an established pattern that would suggest hiring younger versus older has a better or worse hit rate.
On the older side, there have been a lot of coaches that got their first head coaching position late in life that turned out to be pretty good. I don’t think you see much “elite” success from this group because the Alabama’s of the world aren’t going to poach your 57 year old coach that was successful at CU for three years after you hired him at age 54.
Sonny Lubick is an example of good HC that got a shot late. Ralph Friedgen was probably one of the better head coaches at Maryland over the decades and was known for getting passed over. More recently, Sam Pittman is in his 60s and looks to be doing ok at Arkansas thus far.