I don't remove the product unless it comes off naturally when I wet my lips.
E.g if I've eaten and it simply turns white with contact with the water when I rinse my mouth ill simply clean all the food off mouth and lips and let my lips air dry somewhat, then apply more.
I do not stick to the 4 hour rule, those rules were created for hands in mind that probably wouldn't see as much interference with the product as our lips do. The breathing, constant opening and closing of lips, speaking, eating, all leads me to apply around 2 times an hour on an average day.
If I'm at home, I can lower that to 1 an hour but I'll always reinforce the barrier.
With one layer you simply cannot tell its there, but for me 1 layer is not enough piece of mind to tell me the skin is adequately protected.
The truth is, everything will get ruined at parties, like mine just did, but it's fine man. Enjoy your party, use aquaphor. If you go with GIAB on you will have a shit time worrying about your lips like I did.