We used to rehearse on a weekly basis, even if we had 2 gigs that same weekend. Why am I saying this, well it’s so that if we got dodgy monitor mixed instead of that “can I have more upper mids from the hi-hat in my monitor” rubbish that I see many bands do, we’d be rehearsed enough to do the gig with no beaching & whining. I hate seeing bands, after every song complain about the monitors. I used to give the sound people a mic-chart detailing the line-up and what each of us wanted in our monitors as well to try and combat this.
The other thing that really annoys me is bands complaining “why don’t you all move forwards/come down the front of the stage”. They would, except you’re shyte. Rehearse a bit more and focus on the songs rather than the backstage beers.