Or you could assume the band is pretty busy working. And if the band is busy working, then you can look up where they are playing and check out the band to see if it's something worth getting involved in. You can also ask around with other musicians to see what the band or members may be like.
I agree. If I am in a band that works every weekend, with members that have families and day jobs, I don't have time for someone who is gonna take a month or longer to learn our set and/or require lots of full band rehearsals to get there. I will repsect my bandmates time by not bringing in someone who will need work to get them up to speed. I don't have time to work someone in, you need to be ready to jump in.
That's if your band has time to work someone in like that. If your band has a sparse schedule or a stretch of downtime, you can do that. If you have every weekend booked with all-nighters, then I would expect you to learn or know most of my material by the next gig, preferably by the next audition. Knowing only 3 songs won't help you do the gig, neither will 10, nor 17. 30-40 is a nice start.
If I'm auditioning someone, I'm not just evaluating their skills, and ability to fit with the band. I'm also evaluating their current repertoire, ability to pick up tunes, and be prepared.
Nowadays, I don't audition much. I'd rather work with guys who I know can jump in and do the job.