I personally have not had an issue with needing to flush. I am only on my first grow though, but have not seen any negative side effects. I amd just starting my flush now for the first time, for the last 2 weeks. I put a 75% nute solution in every watering and it seems to work just fine, if not more than fine. They are small trees, it feels like walking into a forest every time I enter my room lol.
Like they said, you don't need to flush unless you are having issues. I check my PH every week'ish and have never seen any issues with it. I only have strips, but they always look generally the same color. It is surprising what weed plants can take abuse wise and just keep going. Just don't go to many nutes, lowball it and it should be fine.