I would leave it overnight, that's more likely the reality-that you go to bed without realizing that there was something left out on the counter.

When I was stain testing unsealed marbles, I found they were pretty much stain proof in that if I were willing to use stuff like Comet (and I am!), they'd come clean. Etching is the thing--can't stop that. Also check oils. Serpentines (sometimes labeled "marble" seem to soak it up. I wonder if sealing would help with that. (I'm still using plywood...dang...everything stains plywood!)

Before installing Imperial Danby, I did the same test on unsealed, honed Imperial Danby & Calacatta marble. I did wine, ketchup, mustard, vinegar, & citrus. I was able to remove everything with Comet & a green scrubbie (including etching) from the Danby but not from the Calacatta. There are many on GW that have successfully removed etching with a moist green scrubbie, sanding sponges, Magic Erasers, marble polishes, etc. The one thing to note is that you may change the appearance of the surface of the marble using an abrasive action. In that case, you'd have to scrub/sand the entire countertop for a consistent look. I use a Magic Eraser & have successfully removed etches & water spots without changing the surface. I have one major etch from pickle juice that sat overnight under a countertop mat. I couldn't remove that etch with the Magic eraser. I'm pretty sure I could remove it with the Comet/Green Scrubbie method but I'd have to do the entire island & then reseal. I can't see the etch unless the light hits it just right & I'm looking for it. It doesn't bother me. Here's a picture of the visible etch. It's the horizontal mark in the middle. If you enlarge it, you can see the pattern of the counter mat.

I can't really see any staining or etching on the thicker piece of marble posted in the above test. I would advise getting a sample of the marble you are considering & do your own testing.