Apparently, you can actually burn off so many ketones that there's none left to spill over into your urine.

Water can dilute them, and dietary fat will make them more apparent.

Don't worry if you appear to pop in and out of ketosis. You'll get to know when you're in by the way you feel (for me, steady and not hungry) and (I'm sorry to be indelicate) the smell of your pee.

I always notice that immediately after exercise of ANY kind, there's no ketones showing, but about an hour afterward, they show up because (I think) the fat is still being released by my increased metabolism, but I'm not using up the ketones for energy, so they start to spill over into the urine again. I find the most prolonged effect when I do resistance training, followed by cardio. I see ketones in my urine all day when I do this.