Errr, yeah, what Luke said ^^^^^
Thing is, there might not be contamination in the reservoir but you can't test the rest of the fluid and as it's hygroscopic it could be absorbing moisture and they just found a "fresh" bit in the reservoir.
My 760 has done about 15k in 5 years since the last change but is showing 1-2% water, i've just changed the fluid (and master cylinder!
) on my other beast that has had the same fluid for about the same mileage as the Volvo but was about 10 years in there. I'm 99% sure that the contaminated fluid helped the m/cyl to give up the ghost.
As you can see, it's not so much the mileage but the time that has made the difference.
Also one of my first jobs on my 760 was to change the brake fluid as the brakes felt a fit spongey when i first got it. The difference afterwards was night and day, much firmer and more positive with a shorter travel.
I'd strongly advise having the fluid changed as a precaution, especially as you've done 60k on it.