For the term of their usefulness?

It's my firm belief that most of us within real democracies allow our politicians to serve terms that are far too short.
I recklon most of those we appoint divide (intentionally or not) their term into a basic three sections - a:Getting the hang of things; b:Having a go at making a difference and, c:Planning tactics for re-election. Same theory applies to governments as well, except they have an additional section entitled "Blaming the last lot."
Not that I really blame them. We hardly give them time to realize that they can't fulfil their promises within one term before it's time to start campaigning (or setting up a nice directorship in commerce). They really are only human, you know - no matter what they say.
Four year terms? Why not make it six, or eight? Let's put them in for the long haul, so they have a real chance to make a difference, or have take the blame for failure. Besides which - wouldn't it be nice to have a year or so more without campaigning?
I think most of our politicians enter parliament wanting to serve their state or nation. But lack of time and accountability, and political practicalities make that very difficult.
A friend of mine once assured me he'd never met a politician (singly) who wasn't convinced he was doing his level best for his electorate. "It's when you get two or more together that the rot sets in." he reckoned.