So one thing that always struck me as kind of odd was when you depart a class D tower (VFR) and you get your departure instructions, that's kind of ... it. You just go on your merry way and switch off frequency whenever you want to.
Do people just stay on the tower frequency listening until they're outside of the airspace? Or do you give the tower a courtesy call (N123 leaving the class D) when you get to the boundary, and then switch off?
Or, is it legal to switch immediately to another frequency as soon as the tower says 'left turnout approved, resume own navigation'? It always seemed a bit of a hole to me. But, are controllers bothered by a extra "check out" on leaving the class D?