Feeding from a reservoir, questions. Tank longevity

I've always mixed my nutes 25 gallons at a time. 1 tank for veg and one for flower. Each tank has a pump for watering (hand watering hose style) and a powerhead that keeps it constantly mixing. I use each tank till it's gone. I don't top it off with fresh water or any sort of add back. Just make a new batch each time.

So, I was just talking to my nephew who's worked at many grows in Colo., and he's telling me I need to make a fresh batch every 2 to 3 days. To not make such big batches that last so long. The flower tank normally takes about a week and the veg about 2 or more. He really wasn't able to give me a reason why he's stating this, just that's what he's been told over the past couple years.

I use Masterblend, calcium and magnesium. So nothing organic or alive in either tank. Just 'salts'. I set my pH and never have to mess with it..

Does anyone agree; my tanks shouldn't be used after 3 days or so? Any why?

Thanks everyone!!!

If it ain’t broke, don’t fix it.

Some nutrients will precipitate and drop out of solution as solids making them unavailable. That may be true for the nutrients that were used at the grows your nephew worked at. You will not have that problem with what you're using so continue as you have been.

Every grow is different, different water characteristics, different nutrients, etc. He may very well have needed to change his res a lot based on his particular conditions, others don't have the same issues. If your plants are happy, the proof is in the pudding. I agree with the others.

I'd say you know what works for your system.
just nod and smile next time he says that.

'if it ain't broke don't fix it'... I hear that!
I wouldn't say my plants are perfect. I get red stems and shitty growth from time to time. My hope is, it's due to using shitty coco. Which I have recently switched to Sunshine #4.
thx!