Music Bingo Coverall

I've recently been asked to make a new variant on music bingo by making a separate coverall/blackout set and I'm wondering how many songs should I include in the list and how many calls (song plays) is just right (35, 45, 50?)? I want to have a winner every couple of weeks but not every week so we can have a roll-over jackpot.

The music bingo cards are set up as 5x5 with a free space and have 75 songs that are randomly placed but not constricted like in traditional bingo (B=1-15, I=16-30 etc). This is all done in excel with a formula to randomize the squares. It does pretty good in that with 200 cards we don't seem to have any duplicate lines. Even if we have 2 winners in a round their songs always seem to be different by at least 2. The average now is between 25 and 30 songs to get a winner depending on how many cards are given out and using traditional scoring (row, column, diagonal, or 4 corners).

Thanks for your help.