I agree totally, and the more reviews you have the harder it is to keep the 5 star over the many years of having all types of customers.
I guess I will also be at a 4.9 for many years to come. I also have been getting all five stars and it is terrible one person can ruin it based on something that is subjective like "value". It depends on whether they have traveled in other Airbnb's and have something to compare to. I just had a newbie give me a "4" for value.
And she left five hours after my check out and claimed her son had taken off with her keys. Funny how when the son got back they still too their sweet time to leave after taking showers, etc. Never told me anything until after they left. Lucky for me I really did not need them to leave since I had two days before the next guest, but it was really worrisome wondering if they were actually going to leave or if I was going to have to go over there to tell them to leave...they were ghosting all my messages and phone texts.