I agree with most of what you say. Just fly it if its full and don't worry about how long its been since it was charged.
However, you are incorrect about the battery not having memory. They do, in fact, know how long its been since the prior charge and record additional statistics including number of times charged. These are fairly sophisticated units as far as batteries are concerned and more then a simple chemical battery; they have circuitry and a micro-controller and indeed have flash memory. This is how they "know" to auto-discharge after a certain number of days.
I agree.
In addition - I have five batteries and use them in sequence, with the discharge periods set to 3 days. I am also more intelligent than any battery. If I want to fly and the next battery in the rotation is only showing 3 LEDs, I make a conscious decision based on my intended flight. If I plan on doing a 5 minute test for example, I will use that battery and take off and fly gently, and if I want to fly a full mission I will either top up the battery or use the next one in the cycle, depending on time available.
Most often, it is the burst of full-power with batteries which are not fully charged that causes the voltage drops responsible for so-called critical battery conditions.
I fly a lot (well over 2 million feet on GO alone), and I have never had any unexpected battery issues.