Yes you do worry but only from the heat of the sun. If its really hot (like in LA 90-100) then yea I say do them in increments of shorter times. This will cause for more sessions and more time for the sauce to work but seperation from the sauce. No that wont happen. Use some ice packs inside the shoes to help with the heat also. I use the Air Legends Ice bags here's the link
http://airlegendsla.com/collections/sole-products/products/air-legends-ice-bags
I have had some traction loss but not bad at all. its minimal if you ask me but some others may have had more so I say keep asking but I havent had major traction loss. Also most if not all will cause some kind be it minimal or not but thats just my opinion.
Sole will yellow again its just going to happen. It's all on your wear and tear. Its going to happen. Again this is my opinion from the work Ive done but the process of yellowing is not any quicker because of the sauce.
Hope that helped. I use airlegends products and I use angelus also. Its your preference on what to use but those are the 2 companies that I generally deal with for all my restoration/custom needs.