Sediment in the brake reservoir

[MCB]

Have any of you experienced this milky substance at the bottom of your brake fluid reservoir.
My brakes work fine and my bike is not due for a service for a long time yet.
On a ride it all mixes up then settles down with this sediment at the bottom.
Should I replace or leave until the next service.
Could it be water, then again if water could get in I would see dust around the cap
where it would be damp and its not.
Help! ???

 

[Piston Pete]

 

[katana]

 

[Tweetie]

 

[lecap]

 

[RobCrouch]

 

[MCB]

 

[Titanic]

 

[Bill the Bong]

 

[Moondog]