I don't really put any kind of review score guidelines anymore. But what seems to work for me is if it's a guest that stays for a couple of days, and I have the time, I will ask if they need anything and if everything is fine.
Kinda like when you go to a restaurant, and after your meal comes, and they come asking if everything is good etc. Usually when this happens I will tip higher. Like if I normally tip 10% for basic service, if they come around and ask if everything is okay I will tip at least 15% or more depending on value added service. The reason I will tip extra for this is because this is also when I can give my opinion or feedback on the steak or whatever. Like if I think it's been cooked too raw or w/e, and sometimes the waiter will offer to remake my steak and stuff. So I think this is a crucial part of the experience when you dine in a more upscale restaurant, and they also consider anything under 15% tip to be a fail just like we consider anything less than a 5 star to be a fail.
I think airbnb hosting is similar in a way. Even though 5 star review is what's expected, if you provided value added service it is appreciated.