Hi
I'm Thinking about bleeding my Hope tech x2 brakes when I get some new pads this weekend (not done them in >2years riding). I've got some Dot 5.1 fluid but opened the seal a year ago to help a mate sort his brakes out. I seem to remember reading that it degrades over time or will it be fine in it's bottle with a lid on tight?
DOT fluid is hygrophilic so it absorbs moisture when exposed to air.
If it's a full bottle that's had the lid on tight like you say, and been kept in a dry place it will probably be ok. Worst case any water will boil on a long descent and you'll have to re-bleed with some new stuff 😯
e: I would risk it... but it's not expensive stuff.
I've had mine open for a few years now and I'm still here, have thought about putting in microwave to try and boil the water out. I wouldn't worry about it too much.
Many thanks - will give it a go in the brakes