I've had the 3 in 1 on my car since July, applied after a full correction.
During the time I've had it on there, I've used regular car wash or their Brilliant Finish Rinseless wash as to not mess with it as I was curious how it would be long term. I did top it once with the Foaming Poly Gloss.
After winter, you can tell that it's still there on the horizontal surfaces by it's water beading behavior even when the car is dirty. It's been great in regards to bird bomb protection - I left one (that landed in a spot that wouldn't bug me) to bake in the sun a few days to see how it would do and had no issues with etching. No troubles with water spots. You don't get the insane instagram water beads, but I'll trade those for the real world results I had.
The vertical surfaces you can tell are in need of decontamination - water behavior there is pretty flat. Not surprising after a Minnesota winter. This March when I washed the car I followed it with their new Ceramic Speed Shine - really made the car pop, but you can still tell it needs a decon. Before I do anything else, I'm planning on trying their Foaming Surface Prep to see if it brings behavior back, otherwise I was gonna try claying the sides using the Ceramic Speed Shine as lube. Should be interesting.
Best part of the 3 in 1 is how easy it is to use, so even if you used it as a drying aid every few months as a booster (or even just did another application on a dry car) you're not in it for much effort or money in product. Just my thought anyway.
Regarding the ONR, in my opinion the 3 in 1 will pick up the behaviors of ONR. I've never really bought into the concept of coating products "Shedding" whatever product you put on top of them, so in my opinion you'd have ONR's habits until it wore down, then you'd get a version of the 3 in 1. (I also don't really view the 3in1 as a coating).
I personally found ONR to be "stickier" for dirt when I'd use it for a rinseless wash, meaning that I found the car got dirtier faster when I was using ONR vs alternate rinseless products. Could just have been my experience though.
For what it's worth, I did Gyeon Cancoat on my wife's Q5 around the same time; while I may try to do a decon on hers as well, I'm probably going to switch hers to the 3 in 1 for sheer ease of use.
Hope this helps.