I kept a few long ago during undergrad years, and sometimes look at them but not much. Those days the books were much cheaper though. These days I just sell off all my books to get back as much as I can recover. If I really think the book is special, I'll just go to half.com and buy the same title five years later, at which point the $150 book will be worth like under $5 since it will be an outdated edition by then.