No code for heights of switches, sometimes it is beneficial to keep them higher like in your case. When you install a gas funrnace with a disconnect its benefical to keep them higher for little kids don't play with them.
I've installed all my switches and even some plugs at 4' - it's a comfortable reach, easy measure and also ensures clearance above any future furniture, cabinets, tables and so on. It's also well out of reach of little ones. And, if you're standard when you do your work, it makes cut-outs in drywall easier to measure for.
At this present moment in time I am making cabinets for the kitchen - just in case you wanted to know what I'm doing when I'm not around.