My iPad has over 1500 songs loaded into OnSong that we could be expected to play. We have a standard opening set that we use to read the crowd, then at the set break we decide on 15-20 songs for the next set. This continues until we have finished our 4th set - and any extra time that we want to play depending on how respnsive the crowd is. Our last set usually contains 20-30 songs that the BL could pull up easily.
Saying that you know 30 songs and don't need any help on stage is great, but we are playing different shows to entirely different age groups. One dance might be people in their late 40s to their 70s who want an evening of Patsy Cline, Johnny Cash, Merle Haggard and Waylon Jennings. The next night might have 70% of the people in their mid 30's who want Bob Seger, Tragically Hip, Tom Petty and Robert Palmer.
We can choose anything from some late 40s swing (we do a stripped down version of Glenn Miller 'Moonlight Seranade' for our oldest listeners) and 50s rockabilly, to 70's classic vinyl, through 80s-90s rock. We do a handful of rock and pop tunes from the new millenium - not much admittedly; maybe 30-40 songs that we pick from. But our meat and potatoes is classic country from the 60's through until today, depending on the artist. We don't do Bro-country, but pretty much every other genre is wide open. But there is zero chance that I could ever remember all the songs that our BL will pick - in some instances, I've never heard the song before, but I'm expected to find the tempo and the feel, and read the chart without the audience knowing that I've never heard it.