It would be nice and probably something that will be mandated in the future, I am guessing. With that said, I have vaped older
ejuice without anything negative happening. Some juices do improve with age for sure, and it may darken, but it hasn't seemed to cause any ill effects (although, I do try to keep track of the age of my mixes, but as I DIY it's unlikely that they will be sticking around forever in any case.... Usually when I get to about half-full on my mixes, I know it's time to start steeping again.
So, while I think it's a nice idea I'm not sure this will be the case for all e-liquids until it's mandated to be.
Anna