Stairville ULC03 Aluminium C-Hook

Have been using these for 2,5 years now, and although they don't show signs of breaking they get harder and harder to get off the lighting stands after the show. I guess it's something with the aluminium threads that make them lock up..?
I would definitely recommend these for more or less fixed equipment, but for stuff that goes up/comes down every gig I would look at other products (as I will for the band).