I learned from a few friends thats its not bad to pull your bucking off and let it soak it silicone oil every once in a while, just making sure to wipe it off completely before puting the bucking and sleave back on. Just like any other rubber it will dry out and crack over time, just like stated before. However when I was new (I guess I still kinda am
) I sprayed a bunch silicone spray into the hop up, I thought my aeg was bunk for about a week, then I pulled it apart to find my hop up nearly dripping with oil, so after a quick clean and rebuild, it shot wonderfuly!