For a dubs player, a ton of height over the net is not good unless it's lob height. I say aim for shoelaces unless you are in a cross court rally as the server or returner. Then you're mainly concerned with angles and looking for a way in.
My net clearance in singles play is several feet over the net or more unless I'm looking to force something or win the point. In dubs it's probably 1 to 2 feet or less.