I've only used it once, and on a daily driven/garaged at night car, it lasted over a month. I don't see why you can't top it with a spray wax or even other type of wax if you wanted to, to layer or whatever.
I have used it as a LSP and I also have topped it with #845 and also BFWD no problems so far. A little over a month on a DD outside 24/7 Jeep as a LSP.