For me with the Bars and Chains, I have made them last a long time, but sometimes it's the same as the motorcycle sprocket n chain ratio. for every 2 chains replace the sprocket and bar, or resurface the bar, using a bar rail grinder and in some cases a bar rail closer, get burs and grind nice and true before putting a new sprocket and chain again. When you find the bottom of the chains are wearing too quick so whatever you do to the chain, and at times filing one side more or less to accommodate but after that , Im changing the bar because it doesnt make sense for me to take that extra time trying to save a bar to just reduce the wear life on chains and sprocket. Pay attention to the Oiling and chain tension as well. not enough oil, black bars smoking too much heat, and too tight or too lose can lessen your bar and chain life. I have never changed a bar tip ever? the only reason I would think to change a tip is in case you damage a tip? so not to have to replace the whole bar? anyone have another reason?