I understand once a container of Brake fluid is opened it must be discarded because it attracts condensation.
What if the opened container is vacuum sealed?

 

Is it really worth storing it though? Just buy what you need, and don't keep any left over.

 

Should be fine, i think they have shelf life's of a couple years if in a dry/cool place. Now if it was not sealed or cap left off. Its no good.

Most is so low cost people just buy new and then discard appropriately.

 

When I was more active in my former industry as a creative fabricator, artist & mold maker working with catalyst resins, polymers & rubberized compounds- we used to inject nitrogen into containers of left over liquid materials to displace the air/oxygen before storing.
Aerosol cans of nitrogen; although still available but have gotten expensive since then...and not as commonly/easily sourced nowadays.

I agree with the above comments. While brake fluid still remains relatively inexpensive....

I've also heard that glass marbles are known to work for preserving chemicals and such....?

 

Haven't looked but I suspect the brake fluid container has an "expiration date" on the label. I've bought a number of cans of brake fluid but I never stored any unopened (or opened) for any length of time. I bought the fluid when I needed it and discard what I don't use.

 

if it's sealed I think nothing goes wrong

 

That's an understandable assumption. But without getting up and going to an auto parts store to check out the brake fluid can label I suspect the fluid maker puts an expiration date on the can. (I seem to remember seeing oil bottle labels with an expiration date.) If so this suggests there is some degradation even in the sealed can. Sure the expiration date may be a number the fluid maker pulled out of the air but there might be some justification for it.

Since I have never stockpiled brake fluid (or oil or other vital automotive fluids) I have had no experience using brake fluid (or other fluids) past the use by date. The fluid(s) may be ok. But I have no desire to use my cars as test platforms.