it dries them up. WD-40 sucks moisture out, thus bad for o-rings that require moisture for a good seal.
__________________
"so persuasively did they talk; and yet there is hardly a word of truth in what they have said."
Plato, Apology
"On life's journey faith is nourishment, virtuous deeds are a shelter, wisdom is the light by day and right mindfulness is the protection by night. If a man lives a pure life, nothing can destroy him."
Buddha