Four years?  At best two years -- assuming the Democrats can retake the Senate this year, Clinton won't be impeached until her (mis)management costs her party both houses of Congress again in the midterms.  At which point impeachment by a Republican congress becomes more a matter of when, not if.  The largely irrelevant question is whether that impeachment will be hyped up political maneuvering, or for cause.  Given the void where any sense of ethical or moral compass should be in both the Clinton's, it's probably a 50/50 toss up at best.  (For those fearing the Trumpocalypse, however, also do not fear -- if he's elected and starts going off the cliff he looks poised to try to take us over, Republicans are probably happy at the prospect of impeaching him as well to get the party back under their control and get a noxious puppet like Pence in office, who, to be fair, seems just normal level repugnant rather than the towering, lofty heights of disgusting HRC and Trump aspire to.)