Good call. This is why I don't like to "top off" brake fluid. It should be full with new pads, but it will never empty itself unless there is a leak. Under normal operation, fluid level serves as a quick-n'-dirty pad life gauge.
Of course, if the fluid is dirty, this would be a good opportunity to change it.
1995 Mustang GT (5.0), daily driver
1995 GMC C2500 (5.7), alternate daily driver