The concept of too much is very vague. Like it all depends on the situation at hand, what it is you think you have "too much of", the value of the item, and so forth. . .
However in my opinion that is more for the quantity in actual reality. For Minecraft, you can pretty much have infinite of something, which sets the bar for having "too much" too a really high number.
For instance I have practically mined in the game for most of the time I've played on Dogcraft, where I have mined over 200,000 blocks of just stone, where I have collected a lot of it, but most have been despawned. But I think that is not a lot. Since stone is what consists about a good 65%-ish of a Minecraft world's Overworld. And most of the rest being the air.
Sooooooo. . .. no that is not too much nether quartz ore. That is not enough to think of as too much.