Even with a Nugs-subscribtion you are not certain of a lifetime supply of these concerts. A good example is the music that was removed from Spotify (some of the musics we do like, eg. Nils Lofgren, Neil Young)
I do not have a nugs subscribtion, but I am sure, if I had one, I just stored my collection. However. I also read you have transferred your collection already to HDD, or other media, which is already a valid backup in my opinion. I hardly buy the physical music anymore (except a few artists I really like and deserve my support by buying their music).
So that said, toss the physical collection, especially since you have not played any of it in years. It's the same here, and I should actually listen to my own advise ;-) Though I do not miss the space it occupies, therefore I may as well leave it there to linger.