My 2003 WR450F rear shock is leaking just a little bit of oil, it only leaks after it sits from riding, and it doesn't start to leak for a couple days after riding. I have never had the nitrogen recharged and I think it could use it. I have heard that sometimes a shock will leak if the nitrogen isn't at the correct pressure. Can anyone tell me if this is true?? Also, how often should the nitrogen be recharged?