How long should a promo mix be?

Hey r/DJs, I was a DJ for about a decade and stopped to focus on academics and my career. I'd love to jump back in the game and play out again.

I want to make a promo mix to show venues I can play warm-up and peak time sets, but IDK how long it should be. I'm thinking at least an hour, maybe an hour and a half, but no longer than two hours.

How long should my promo mix be, and what general advice do you have for getting my foot in the door? Some ideas: I have a large network I can invite, offer to play for free....