It doesnt take long. Literally a few seconds.
I think this is the "money" quote.
To start, I don't think we're talking about a pro touring band situation here, though it's not stated either way, and there's nothing in the Op's profile. As a weekend warrior, I can set my sound in literally a few seconds, and I don't have a complex pedal setup - just a few effects which I rarely use, and an EQ, which I always use. And yes, I need a few seconds to play a few notes so I can hear how my bass sounds in that room. You know, play a few notes at volume, make a few tweaks, play a few notes to confirm, and done.
There's been a few gigs where I likely should have taken a little more time, maybe 10 or 15 seconds to dial everything in. One, a couple of weeks ago, where we were set up in a corner on a low stage, and there was this weird resonance going on around 55 to 60 Hz, and every time I hit a note anywhere near an "A", it sounded off key. The first song or two we played sounded weird, but I was able to make adjustments as we played to fix it. The weird resonance wasn't picked up by the camera recording the gig, but the guitarist mentioned it after our first song. I think it was a stage vibration or something.
Here's a pic of the stage:
Anyway, a few seconds of sound testing is fine in my opinion, before the sound check, even at a restaurant while people are eating. Any more than that, it becomes annoying.