My bike's manual suggest that I shall change the brake fluid and the suspension oil every 2 years. I am curious if it is really time dependent (i.e. do these fluids go bad with time) or use dependent (and 2 years is a good approximate for an average user). I plan a long journey right as the two year mark comes along. In the previous 2 years I have not used to bike a lot and I do not have a lot of kms on it. Most of degrading currently on these fluids would be due to time and not usage. I am curious if I should change these fluids before or after a short duration of intense usage.
The brake fluid is hygroscopic which means it absorbs moisture over time - this degrades its performance and it may boil under arduous conditions.
The suspension oil can degrade with use or time and the compounds or additives become less effective.
Good maintenance is the best thing you can do for your bike (or car etc), preventative maintenance is expensive but repairing breakdowns is even more expensive...