Some artists seem to have a different sense of what is fun from the mainstream culture.
Run for them goes on in their head, in their daydreams.
Fun, for me might be knowing the names and conditions that different plants need, memorizing their heights, colors, bloom times and so on. Or enjoying finding out everything I can about pigments or mediums.
My grandma has made several hundred wool rugs of various sizes. My uncle collects International tractor models. My aunt makes stitches over and over and over in a type of handwork called Hardanger. My son re-makes his bike over and over in different ways. My husband has competed in a couple Iron Man races which means he swims 2.4 miles, gets out and bikes 112 miles, then puts the bike away so he can run 26 miles. It takes between 12-13 hours to do so.
To all of us these things are a really good time, and it keeps us from making trouble. We also have something to show for our free time after it is over.