Lets do our homework...If you take the whitburn book between 1965-1995..which is the span the author hinted as his target......I will bet a dollar to a donut that there are over 3,000(conservative estimate) top 40 hits (that's top40)which is standard of top40 radio, what about all the 40-60 range cuts that are the staple of programming lists.....to say 2,000 represents a MUSIC GEEK or RECORD COLLECTOR repesentation of everything ever recorded is plain ignorant and a simple regurgitation of ""so called experts" defending the theory that any thing over 1,200 is no good. Sure go with 800 - 1200........... like listening to a six cd player on repeat. And on an A/C format you can draw from every chart on Billboard, the possibliities are endless ...but, no, more than 2,000 is toooooooooo much,bunk. I say Bunk. A/C in the only format where a span of decades and different genre's works great....so far evryone wants to pigeon hole you......... from some hip 50's/60's "Sinatra" to 2010 "Buble", Tony Bennet "San Francisco", 80's Wham-"Careless Whisper", 60's Ray Price.."For The Good Times" , 70's Sanmmi Smith "Help Me Make It Thru The Night"good music is good music, universal appeal, 60's beatles, 70's soft America and Al Green-90's Amy grant and Celine Dion back to 60's Gladys Knight,stylistics, del-phonics, Elvis "can't Help Falling In love"(Elvis had 104 top40 hits alopne) , soft eagles, crosby stills, nash, every Instrumental from the 60's-80's, I could do this till my fingers bleed , but, no.......2,000 songs are for geeks only.
A/C doen't have to be a narrow a format as the rest, It's wide open ....but hey I'm a 4,000 plus song playlist guy, the 800-1,200 theory is outdated, and is kept alive by those don't want to do the homework, be creative ......they settle for lazy and boring, programming.