I don't let it sit forever I do my shower over the course of a few days. I spray it let it sit for 5 or so min while I get ready to go in, then I go in and use a scrub brush nothing too rough but not soft either, and go over the glass... then rinse.. next day might throw bleach in there to do the moldy spots, same deal... takes me about 3 - 4 days but this way it is not a huge chore, I break it up in stages, and cause its new it cleans up quick. I hate to clean so I get in get out....my stone was sealed by a good quality penetrating sealer many times, then every 6-9 months. So I have no issues with any of the areas being damaged. If you are afraid of yours being effective get a piece of scrap from the installation and play with it. But make sure your treating it the same iow if your shower is sealed, then seal the sample piece. My shower actually has two different kinds of marble and one is Naxos and it is super soft... but This is around windows and Niches. Anyway this is how I do it. Yes they brought Jubilee back! It is the same, just smelling it brought back memories of cleaning the toaster.... lol

I would do a search here for the following terms: "marble on shower floors" "marble stains" "iron stains in marble" "marble not drying" If you do a bit of reading, the common result you will see, is that marble is not the best product to use for shower floors or walls. My master bath was all done with tile from Walker Zanger, but I used their porcelain and glass tiles for products that are durable and easy to clean. I am willing to squeegee the whole shower after I use it, but not something that my husband or kids would do, so products have to be chosen with all family members in mind. I am now doing 3 more bathrooms, but went with a competitor of WZ in my area, as they have many of the same product lines, but had better pricing.

I would try to find a porcelain mosaic for the shower floor too. Based upon the number of threads I read in here about natural stone including marble that absorbs water, darkens and is always damp, I would be hesitant to use it on a shower floor.

June - I am installing marble in my master bathroom remodel - demo begins on Thursday. The issue I’m struggling with has to do with using the marble mosaic tiles on the shower floor. Apparently, there are some marble tiles that absorb more water than others. This causes discoloration in the floor. There are several threads on here discussing this issue in depth, including articles linked by a professional contributor here on Houzz - Star Tile & Stone, LLC - who did in depth research on this specific issue (Google “Porosity of Building Materials and Marble Moisture Discoloration“ on TilePro-USA.com). Using cheaper marble may increase this issue based upon what I’ve read. I’m not sure how often this actually happens - people don’t post when their marble mosaic tiles don’t absorb water unevenly. It has caused me to look at a few other options - but I am running out of time to make a decision. With respect to all of the other issues, there are MANY discussions on here re: pros/cons of using marble in bathrooms/kitchens. I have been to Italy several times, and have stayed at many OLD hotels with marble bathrooms. I don’t really recall seeing issues - and there had to be, at least, etching in those bathrooms. Also, I’ve dated a guy who has marble in his master bathroom shower - he doesn’t squeegee his - and he doesn’t restrict the types of soap/shampoo/etc used in it. His shower always looks very nice (and is really why I have wanted to install one in my bathroom). I understand why you’re concerned about using marble - especially, in a bathroom used by a child. Unfortunately, you won’t get a definitive answer to your question - because there isn’t one.