How often does PSA update vintage prices in the price guides?
I collect mainly vintage (1910-1960) PSA graded hockey cards. I've noticed that the prices in the last few years have increased significantly. Several years ago, I used to be able to bid at 110-120% of book value and get the items. Now, I'm seeing auctions regularly fetch 150-200% of book value. This is especially true of pre-WWII cards.
However, the PSA price guide hasn't moved on these items in years. Does PSA ever change vintage card values very often on other sports? I know vintage hockey is kind of a niche area. Still, it would be nice to see the price guides updated at leave every few years.