it's dependent on the quality of the spacers and the machining of the hubcentric rings. If they don't seat well, I can see how you'd be able to tighten them without having them fully seated. Then if you drive, the rings will wear and everything will loosen.
I've run spacers for quite a while, and I always check that they're properly seated when reinstalling and torqueing.
Decent spacers should never cause issues like this though.