I know this will seem counterintuitive especially in light of what you are seeing but some realities;
Known Degradation Mechanisms
extended periods of time at extreme High/Low SOC
So those are your tools.
sounds like time is the least convenient and in light of Nissan's new battery exchange policy for out of warranty packs, could be your downfall
So Heat is one thing. you only need to QC a lot. Like 5 times in a day. That will take a lot of driving but I am guessing the cycling/miles you have plenty of...
So despite what appears to be happening when you QC, its not. Your pack still must be tested for degradation no matter what the car says. I can only remember one for sure, maybe a few more that had lost their bars, took it in and failed the degradation test. (they did pass the test a short time later) There are other cases when the last bar disappeared only to reappear a few days later. rarer, but not unheard of.