depends on the particular ball joint etc.. at the least you need to remove the balljoints from the spindles occasionaly, grab the stud and wobble it around. it should have a little ristance/stiction if it moves really easy it's time to replace it.
oh there all tight. they look pretty beefy and non are loose. so nothings just going to go if its not loose? like its a simple check to see if its going to fail?