It depends is the short answer. My "gotta ride, but not all day" or even half a day is about 16 miles and takes me about an hour, give or take a couple of minutes each way, depending on how I feel. If I have more time (less other things to do), I have some 20-25 mile routes that are close.
Longer rides are anywhere between 25 and 60 miles. Although I have done several metrics and one century, I rarely ride over 65 miles. In fact, I never rode further than that right before I did my century.
Of course, if I am riding my bike to do errands, some of my rides are as short as 8 miles.