IMHO music "testing" has been misused. It is good to play songs that "test" well, but just playing the safe "hits" leads to burnout. One of the reasons top 40 worked back in the day was it changed. Sure the songs were burned out, but they went away soon. If you look back at most top 40 charts, 30 or more of the songs were gone in 60 to 90 days. I sure some will find an exception, except for January, once a song peaked it was usually gone in 30 days. If I were musically programming classic hits, I would start with Billboard's annual top 100. Play all of the songs except for novelty songs which should be put in separate request only once a week maximum category. So if you are doing classic hit 70's and 80's you would have over 1800 to 1900 songs in rotation that should be recognizable to the average listener. Of course you should have a good mixture of the years so you do not get too "old" or "young".