Sometimes it's nice to just spin. If you wanted to get there fast, you could drive your car, right?

With fixed gear, having a ratio either too high or too low can make BOTH climbing and descending more difficult, as I'm sure you've found. Still, it's usually best to err on the side of too low, especially if most of your riding is on generally level terrain.

As to your age comparison, I think there should be an inverse relationship between age and gear-inches. I'm 46 and like to do most of riding between 75 and 85 GI, but I won't be surprised if that number decreases as my age goes up. Maybe they'll converge in my 60th or 65th year.