Hi All
This is an encouragement to do the job. I've been carrying out a 16K service on my 1994 (yes, I'm only the second owner) Yamaha XJ600S.
I didn't replace the brake seals. The old fluid was clear, no suspicious black dots. I just flushed through until the new fluid showed.
The braking difference is considerable. If you haven't replaced the fluid after 2 years I'd advise you to do it.
Safe riding
JohnnyDG