A lot of it is dictated by the weather. Earlier this summer, we had four straight days of rain and the grass loved it. By the time it was dry enough to mow, the grass was knee high in parts of my yard.. I try to avoid that. My yard is usually mowed every other week.
With all the rain this spring I mow when ever the lawn is dry enough, if I don't the dog won't go out, she hates wet feet.