Random question, but how long does brake fluid last, in an unopened bottle?

I've had a few bottles of this Valvoline Dot 3 & 4 synthetic fluid, sealed in an unopened bottles for about 2 years, possibly 2.5 years. I used it to bleed my friend's brakes today, and we ended up flushing the fluid completely.

His fluid was dark amber but came out clearish yellow, and the fluid in the bottle looked and smelled new/clear

I am sure it is much better than the 7 year old fluid in his Yota, but it got me thinking if it was still "safe".

I now have about half a bottle left, but ill probably dump it if I don't use it soon, unless everyone else calls me a pansy and tells me to use it.
And I think I still have an unopened bottle left...

 

To know for sure get some brake fluid test strips and use them on it.