Sorry if this is a dumb question but always wondered what the purpose is behind the "At least 18 in a row" moniker. Oviously it sounds great that your playing 18 songs in a row, HOWEVER I have heard a few stations that use this and don't play 18 in a row, they stop down 2 stopsets each hour. Does it have to do something with the clocks? What's 18 an hour and a half commercial free? Or is it simply becuase "18" is a number that has been researched as a common number, or just sounds good?
It really depends on the station, but I'll take a shot at a brief explanation/assumption:
Regarding two stopsets an hour - The station may not execute "18 in a row" back-to-back all day. It may be once per day part. Or maybe they do 18 in a row, stopset, 2-3 songs, stopset, then kick off 18 again. Or maybe it's once every couple hours, or every other hour, etc. There are many ways to execute such a concept.
I've also heard stations say "At least 40 in a row" which refers to 40 MINUTES of uninterrupted music. It's all in the wording.
But remember: Just because a marketer (or radio station) says something is amazing doesn't make it so.