I highly doubt that KISW actually trusts 4+ days of programming to listener's mail-in ballots. I have some of these lists dating back to the mid 80s, from many radio stations from around the country. To me they are more like a snapshot of what the station chooses to represent it’s self as.
In the 80s, the KISW top 1000 included a strong showing from Dave Mason's "Only You Know And I Know" - a song rarely heard on the station, even then. However, it was important for them not only to be known as The Rock, but to be recognized as the heritage station in Seattle - playing a few occasional deep cuts gave them some cred.
KISW wants to be known as the station that not only plays Rush - rather they want to be known as the station that has played Rush from the beginning. And they drive that point home by spinning Xanadu once or twice a year during the Top 1000. If you look at these lists from year to year, you'll notice that they really do compliment the programming of the era - but they do not mirror it.
KISW probably has about 500 songs in rotation at any time. Xanadu is likely never among that 500. ...and probably hasn't ever been a core track. It was released in 1977 well before KISW switched from the mellower progressive AOR to the Hard Rocker it became in at the very end of the 70s.
Xanadu, in all its overblown glory, is a relatively unknown song, and a difficult listen to the casual ear. And from my experience, Rush fans do not universally love the song. So it's hard to believe mail-in ballots from average listeners, consistently, from year to year, place this track in the top 1000. And if they did - why hasn't the KISW programming department taken the hint by now and incorporated the song into a rotation cycle.
In a recent thread, folks were raving how stations live trend to trend. So again, why, in a business environment seemingly driven by monthly trends would KISW trust four days of programming to a bunch of pesky listeners? These are a smart bunch of radio peeps. Not a quarter hour goes by without some serious evaluation programming. If you are hearing Xanadu, it's because KISW wants you to hear Xanadu.
"Only You Know And I Know" is a better song. Let's start a mail-in ballot campaign for the next top 1000 and see if it makes the list : )