How long before it becomes an issue, how can you tell, and what is the solution? Will I eventually have to toss it out?
Biochar... It's not for me but....
@Azimuth has better actual practical experience with it, so he should jump in here, but here is what I (think I) know about biochar. But I could be wrong.
It appears that it was invented by the indigenous of the Amazon region and they make it by putting organic waste into clay urns, sealing them air tight, burying them, and burning a huge fire over the burial spot to super heat it.
In the high heat and absence of oxygen the refuse doesn't ignite, but it does turn to charcoal, which was called Terra Preta, which translates to black earth. (Or Terra Preta is what they call it after it's mixed with the soil and forms black earth.)
What it really is, is what's left of carbon after you remove everything in the carbon source except for the pure carbon. So it's pure carbon. More or less the same as what a carbon source is like after microbes eat it, but greatly expanded from the heat, so it's very porous like a piece of lava rock or perlite. It's expanded pure carbon.
So it's a humate that can instantly interface with the CEC of the soil and start moving cations to the roots, just like natural occurring humates from composted carbon such as coco, or wood chips, or leaves, or any composting "brown".
So adding carbon to your soil such as wood chips or leaves will eventually get eaten into humates, or you can add biochar instead and instantly have humates.
That sounds super sweet but..... to turn a wood chip into a humate you feed and employ millions of microbes. If you throw in biochar instead you don't need microbes to create it, the fire did already, and because it's expanded microbes can certainly live in it, and it does house them, but it also holds wayyyyyy more water than the carbon from the eaten wood chip ever will. And eating the wood chip creates poop, and that's the whole point here. Creating plant food.
So it's an artificial humate with no nutritional value that does add to your CEC but it holds way too much moisture, but it does happily house microbes, but it's expanded so it takes up space in your pot.
Pro's and con's.
So is it better? No, you can achieve the same but with a proper water retention ratio, and the microbes eat for free while achieving the same, thus creating poop fertilizer.
Because neither type of humate ever really goes away, you can see that even without biochar your soil will eventually contain too much of this carbon, but microbe humates are very small in size when compared, so they don't build up in volume as quickly, and as a result don't over saturate your soil with too much water retention.
So why did the Ancients even use it?
Because the Amazon soil is actually very naturally low on carbon, so this drastically helps the CEC improve, and it floods for half a year and then droughts for half a year, so they desperately needed water retention in the dry season. A perfect fit.
The trick was to not add too much, but it lasts forever and only gets added once, so expansion across the land happened quickly, and farming took over. You add it once and low carbon soil with terrible water retention is immediately fixed.
That biochar is still powering those gardens today even tho it was added a thousand years ago.
So it's a hack. It has it's place for sure, but it's a synthetic and as a result sways the natural balance of the soil.
That doesn't mean it's bad, just that it needs to be managed properly.
I get excellent brix without it, and just like you all, I too have to be really diligent about not getting my soil too wet, so for me, biochar isn't an option. I prefer carbon that comes with free microbe poop.
Not because it will or won't work tho, it's because I don't want to change my system by adding something I can't remove from my soil. You can't flush it out.
Now outdoors if I had some shitty soil I wouldn't hesitate to mix a bit in.
If you add it to your indoor soil you need to track it if you add it every rebuild, or you will end up with soggy soil that will hold that sogginess for a really long time after a few rebuilds.
Also, if it does actually dry out it will become a dry sponge and start sucking the moisture from your soil and roots, so it has a yo-yo ability to it as well. Brix thrives on stability.
5% max by soil volume would be my limit, but even that, dumping a gallon of it into 19 gallons of soil (5%) seems pretty extreme. I'd rather have 5% more food in that space. A lot of food fits in a one gallon bucket. My pots already either barely make it, or run dry and need feeding, so to lose a gallon would hurt me. It would create work. Work bad....
But it will fix shitty soil up really well, and quickly too if you grind it up and till it in evenly.
Got a notoriously dry spot on your lawn? try a bit, just start low and add more if it's needed, because you can't remove it.
...IKR......
Commercially it's a great additive as most don't rebuild their soil, and fresh soil takes a couple weeks for the CEC to start working well enough, so it jumpstarts a soil, but used soil does that too as it has humates from last grow, so you need one or the other to get a good start.
If you never reuse your soil some biochar is an excellent thing.
As long as you understand that you only add it to soil once your good if you don't add too much.
There is also biochar's very valuable arguement that you can, and should, pre-charge it with microbes and nutrition just like wetting a sponge, so it innoculates the soil.
That has 100% legitimate value to it, but used soil does it too, so that claim is neither here nor there if you rebuild your soil.
So again, if you aren't going to use your soil again, buying commercially with precharged biochar added has better possibilities.
Sorry Carmen that's not a direct answer to your question, but I read about it, and saw no practical value in it for how I grow, so Azi is our resident expert for your answers here. He uses it.
It's possible that a small amount will improve my soil, but then I have to track that soil. I'd rather live without it.
High brix is high brix.
Gee is Lazy.
Yup, that's a capital L
.
, and I just happen to have 10 large ziplocks full of fresh frozen RVDV from outdoors. 
