They WILL erode, but it might take 100,000 miles to get bad.
I dont necessarily agree with that. So long as your not building a hotrod motor, there really shouldnt be problem for the duration of the engines life. I know theres plenty of vehicles still cruising on the roads today that havent had a problem and Id guess many of them are well over that 100K mile mark with no issues related to the valve seats.
That being said I really doubt Ill ever put that many miles on mine.
