They could all arrive within 30 minutes but you also have to factor in the larger planes of Air France and KLM, although they are usually a little later.

There is also the possibility of a delay of one or more of the planes. For example, the Delta flight from ALT today is running about 40 minutes behind for some reason.

Typically the immigration part is pretty efficient unless they are on some kind of work slow down but I have not seen that mentioned for some time now. Luggage is usually the bigger hold up but I doubt you would have more than a hour total at most even if all 5 planes did arrive at close times.