I've never given muffler maintenance a try. I have thought about it, but it never seemed important enough to dig into. Now I have approximately 35 hours run time on my FMF 4.1 can, not sure how often is often enough vs just going overboard on maintenance. Sure, I could call FMF, I could check my owner manual for what's recommend, or I could see what the guys and gals at TT have to say! So what say you behind the keyboard bike mechanics? Is there a change in resonance that could be heard or felt? Do the repacking intervals get closer together if ridden WOT more often that putt-putting around or vise versa? Does running rich or lean affect how long packing lasts? All I know is that I know nothing lol.