Some casting directors callback every actor that delivers a half-way decent performance in a casting room, while others only invite back a small handful of actors that absolutely killed it during their audition. So what's the right formula? Well...somewhere in between.
On one hand you don't want to pack the casting facility with actors if you're holding your second session and suffer from information overload. Casting, after all, is a linear process, and you do have to eventually narrow your choices. On the other hand, if you're too selective in the casting room, you may back yourself into a corner.
Only having 2-3 choices per role is sometimes problematic because sometimes, you see something in the callback that you didn't see in the casting room during the first session. Other times, all 3 actors that you've labeled as contenders to play a role may all be out of town, or maybe chafe at the material once they see the full script.
The point is that it' better to be safe than sorry, but it's also good to be decisive. Our recommendation? Select app 7-8 actors for callbacks for each role, and naturally expect 3-4 actors to either become unavailable, or perhaps deliver a less than stellar callback audition. That way, you'll still be left with 3 solid contenders, which will then allow you to make solid decisions in the casting room.