The more you put into your plant, the more it will give you.
Plants should never sit in water as the roots can rot.
From my understanding, the purpose for flushing is this: a plant will absorb different minerals/foods at different rates, so after a while A+B might be clearing normal but each time there is some C left over and it builds up.
The issue with this is interactions between what you're feeding your plant. Not only can your plant be getting insufficient nutrients through not enough of one thing, it can also happen from too much of something.
If you're an experienced grower and confident in your nutrient levels, flushing isn't necessary. If you're still figuring out new things, you should flush much more frequently than before cutting. For example when you change nutrient levels, such as veging or flowering, and definitely if you notice a nutrient imbalance.
Flushing before cropping is good, if there are excess nutrients in the soil it will affect the taste.
If you've been growing for a decade, chances are there isn't a lot of excess nutrient in the soil when it comes to harvest time.
From your posts, I'd recommend you give them a flush.