I could be the MC is a little iffy and when the brake work was done new brake fluid was introduced into the system, which rejuvenated the MC.
5-6 years is a little young for a master cylinder to go.
If I had any doubts about a master cylinder I would change it too
If you get the brake fluid replaced every 3 years the various brake components (besides the pads and rotors) will last much longer.
This is especially important on a vehicle with ABS.