Well, we just went VLC to MAD TO JFK on IB (Iberia) and we had a scheduled 1.5 hr connection time. Flight from VLC to MAD was late so we only had 54 minutes total from landing to take off of the next flight. We arrived from VLC at Terminal 4 all the way at the end of the terminal where a lot of the regional airplanes arrive. Then we mad dashed - ran all the way to the 4S train (had to go down two flights of escalators) and onto the LONG (but relatively quick) train ride and into T4S and through Immigration and then all the way to the other end (Gate 47) of T4S. We just got there just barely in time and we RAN fast! Our luggage was not so lucky and did not make the connection. The distance from T4 to T4S is really far so I imagine it takes them a long time to transfer luggage between the terminals. As others have posted, while we got our luggage delivered to us 30 hrs after we landed, dealing with IB customer service is a nightmare! They are impossible to deal with and at no time were able to tell us anything other than what was posted under our reference file number on the online tracking system which was "Delivery Process Initiated". They would not make any attempt to find out the status or when the bags would be delivered other than call us back in another 24 hrs. We are really thankful that we got our bags at home but dealing with IB is a horrible experience.
I would not check bags through MAD unless I had at least 3 hrs especially because flights can be late (like ours from VLC was).