Now I guess I am going to have to go back and check my spades.
(I am bi-wired, so at the amp end I actually do have a pair of bananas and a pair of spades.)
But I cannot ever recollect any of my spades coming loose. I tighten them as tight as I can get them by hand and then give them a tiny tweak with a pair of pliers. I wish they had a hex head, but I guess the reason that they don't is because people would be going ballistic and over-torquing and stripping?