Sometimes the A-check might take longer...for example, at Finnair it took us at least a couple of days to do the A-check for Air Liberté DC-10-30s.....
In D-check, everything that goes off, is taken away from the aircraft (the main hull; the pipe) and is sent to their respective departments. The painting is removed etc. and as you said, takes weeks to accomplish.
One could describe the D-check as a 2-way puzzle: first you put it into small pieces, and after checking everything, put them back together. But it's a one hell of a puzzle
1740 days idle. Beat that.