Much has happened to Craig's Bond in the time between 'Quantum' and 'Skyfall,' that much is certain.
This is not the run-and-gun, fresh to the world of spies Bond that we saw in 'Casino Royale.' This is a version of the man who is bordering on 'played out,' who is held together by his drink and his pills, as Silva puts it later in the movie. This is a Bond that has been through some things and seen some things. Let's have a look at the scene, just as a refresher. One scene in particular hints at the importance of this time gap, which sees Bond breaking into M's apartment after he was presumed dead, given that he was shot off a train and fell to a would-be death in the cold open. If we're to assume that 'Quantum of Solace' also takes place in 2006 (roughly speaking) as follows right after 'Casino Royale,' then six years or so passed between the events of those movies and 'Skyfall,' which was released in 2012. But something else key happens in 'Skyfall' that is easy to gloss over for the average viewer.