I'm posting here because I have a similar question about waterproofing your dress shoes.
I also have been using waterproofing sprays on both my suede shoes and my leather dress shoes (though I haven't seen the spray I use to contain silicone).
What I have learned is that one should apply spray on the shoes about once every six months, or after the shoes have become wet due to rain. But what I'm not sure about is something that happened recently: I applied waterproof spray onto the shoes I'd recently bought, but as I then used them a few days later, I noticed one of the shoes had some scuff marks on them when I came home. So I polished both shoes and the scuff marks were gone. But this made me wonder if I should have applied a new coat of waterproofing spray since I thought the previous coat might have disappeared due to the polishing. If that is the case, that would mean a new coat of waterproofing would have to be applied every time I polish the shoes, which I thought would be a bit much.