In reply to Doug:
> ..., we (the electors) would get confused.
Phrased like this it does indeed sound stupid, but is a real issue in German state elections, which are sometimes but not always run together with the main, federal election.
Historically it can be shown that voters do let issues at one level influence their vote on the other. This is why state governments set their state election dates at the same day if they hope for support from the federal campaign (e.g. office holder's bonus if from the same party), or on a different day if they are e.g. worried that a protest vote against an unpopular government might carry over.
The price is that there is always an election somewhere, which prevents federal government from doing anything out of fear that any unpopular measure might damage their candidate at a state level.
Overall I would support fixed, narrow corridors for regional and local elections, one in parallel with the national election and one or at best two further dates during each national parliamentary term.
CB