This post on Political Betting is an excellent counterweight to the current body of opinion that holds the coalition will last for more than 2 years. At a Policy Exchange event not so long ago around 3/4 of the room (full of professional politics-watchers) - said they thought the coalition would last 4 or 5 years. I was in the minority that thought it would be less than that.
The coalition is undoubtedly being given the benefit of the doubt at present and the public and media seem to want it to succeed. The mood, and media narrative, will change at some point however and I wonder just how far the Lib Dems will go. Are they, as Henry Manson argues, the weak point that might bring down the coalition?
That seems likely to me.