the only thing keep in the fridge is yeast. As for pH buffer solution, vinmetrica reagents, additives such as pectic, nutrient, calcium carb. tartaric acid etc are kept tightly stoppered, in the dark in my home winery, which is about 70-75 degrees. I also keep opti-white and red in the wine cellar as to not let get above 65F. I used to keep my pH buffers in the fridge but got sick of having to think about taking them outta the fridge everytime i wanna use them to allow them to get to room temp. I just observe expiration dates and discard once it has reached said date. All is well so far.
i think extreme heat and sunlight are the bigger problem.
p