I've been collecting flyers since I started collecting in 1988, but it wasn't until the 1996 Pinball Fantasy show in Vegas that I realized that they were actually worth money!! I used to staple them to the wall!!
Since then I've accumulated several binders full, keep them in chronological order by manufacturer, makes for a very interesting pictorial history of pinball. Mainly stick with games starting in the SS era, for EM's there are simply too many different versions and countries, makes completing any sort of collection almost impossible, (not to mention expensive!!)
Like the games they represent, the flyers are like pieces of history, indicative of their time and place, some are even quite creative.