I just sent my 07 yz450f head off to them. 500 for a full valve job with faction SS valves and new spring and retainers. or 100 just to have the valve seats cut. He said his Faction SS valves are custom made for him and much better quality than what you can buy off the shelf. What do you think? The oem valves lasted me a long time. Would the SS ones last about the same?