Regardless of what you say, a public official can be impeached for past actions that occured before they were elected into their current public office or position.
You seem to not understand the issue of Impeachment from a Constitutional perspective.
And impeachment and consitutional are NOT capitalized.
In my estimation, revelations of wrongdoing before the person held office could merit impeachment. Certainly severe criminal offenses would interfere with the work the President was elected to do, regardless of when the offenses were committed.
Of course, nothing I've seen would indicate this should even be a topic of discussion in regard to VP Cheney. Makes for interesting constitutional chat, though.