if you try solo mining you'll find that you hardly ever get "average" results. It'll be either really good results(like you're getting now) or really bad.

It's like the weather, temps are usually either  above or below normal.

An average is by definition just an average of the extremes, you hardly ever see it in real life

That's why you have miners chasing "lucky" pools when they are finding blocks, then looking for another when the "luck" turns bad