I've been doing alot of reading on the site about the G0453Z planer compared to it's counter part the G0453p with straight knives. I know, it's been beat to death, but I haven’t really seen this question addressed. What I'd like feed back on is the longevity of the indexable carbide inserts used in the cutter head. Specifically how much cutting a guy can expect before having to replace the inserts because all four sides have become dull. Assuming no damage due to nails, etc. It looks like it would run around $350.00, less shipping to replace all of them. Do you start seeing more distinct lines as they get duller? Do you turn them one at a time, or address each one as it show dullness? Thanks for any feed back from those that have been using this type of cutter head for awhile.