It is when two spades at once atop one another have to be installed that I find the problems with loosening start. The likelihood of two stacked spades coming loose in time is much higher. My Rel subs require such a connection ("high level,") and I have to check on it periodically. Recently though I added a new power amp to the lineup that made the Rel's play too loud at even low settings on the volume knobs. Rel's advice in this situation is to use only one of the spade connectors and tape the other spade. Much better on all counts
Bananas rule, spades drool. End of discussion.
I just checked my speaker connections. All using bananas, all nice and tight.
The number of times I’ve had spades get loose instead though.....
Point is, and it really is kind of a tongue in cheek thing, bananas beat spades for long term reliability in almost all setups. If you have to use a Cardas or Mundorf speaker terminal to ensure your spades stay tight it kind of proves my point.