It'll wear more than if you didn't use it, but there's no difference in the internals whether it's connected or not. Since generally the hubs can be a pain to service, I'd probably swap it out if I wasn't using it. If you keep using it, make sure to cover and protect the output terminals.
Stupid question: does a dynamo hub ‘wear’ when not connected? I have a spare front wheel but does it matter to switch?