How often do you all change your antifreeze? I use the Spectro premix for the maximum protection for cooling, but I realize Anitfreeze can break down also and not work as good as when it is first put to use. When I first got my bike I was changing it about every 6 months. (Probably overkill) But now it has been probably 16 months or so. I just wondered if it is really necessary to do it any more than that.