Arthur, surely Col. Berman's collecting habits are not unusual for a person of substance in a very prosperous nation.

There have been individuals and families who have been hoarders in America, since before The United States existed as a nation. I think back to the old Brahmin families of Boston and the Knickerbockers of N.Y., N.Y. and the Hudson Valley of upstate New York. Some will call such individuals and families sick, or merely eccentric. Others find them mildly interesting. Some (of these hoarders) recognizing their own ultimate mortality, make arrangements to entomb their soon to be former possessions in museums, where they can be enjoyed
slightly by future generations. Others make provisions in their wills to have them entombed with their corpses, or ashes. Still others leave them to family members (who may sell them immediately, keep them for their natural lifespan, and /or sell them at some point, out of economic hardship, or their descendants may, later).
The main point is we are all very temporary caretakers, of these objects of our creation!
We can enjoy them for our extremely fleeting lives, and that is it. 
At best, people like Col. Berman will be a mere footnote in history, if that (because of his museum philanthropy). And that is okay, because I don't know, nor care , whether I will have one (a footnote, that is).
John, to answer your original question,
I think that an advanced Thompson collector is someone who has spent some serious time acquiring a fairly broad and deep knowledge of all things Thompson (found in books by people like Roger Cox, Tracie Hill, Frank Iannamico, etc. and in other knowledgable collectors found on boards like this one) and has bought/ owned at least one TSMG (any variant). That is why I am not an advanced collector, yet (mine is only a semi-auto). Full-auto is verboten in New Yorkislavia.:-(

Best Regards, Walter