Navrad i was in D&D this morning and asked them about this. D&D will only ask you to call back for a practice if they have an emergency on (remember that they are monitoring two frequencies, 121.5 and 243.0) or if the controllr was unavailable for any reason... including i guess calls of nature!
D&D do have visits - usually arranged (I understand) through "Flier".. and I know that they read PPRuNe!!!!
Mr Chips