Yes, but again, some are more stable than others. As an example, silicate is stable at higher pH. The concentrate pH will be higher than the corresponding premix. The lower pH on the premix will cause silicate to fall out more rapidly. It is not a critical problem, but like I said, a fresh premix is better than one that has been sitting around for a long time.
So when you buy that concentrate, don't just make all the premix you will need for the next few years. Make it as you use it to maintain its quality.