The worst problem with brake hoses is the rubber releases from the inside out and works its way back up the line into the master cylinder. Eventually you start finding gunk in the bottom of the reservoir. So to replace the hoses at 12 years is probably not a bad idea, particularly if you are seeing a lot of discoloration in the fluid.
For as cheap as they are, won't hurt to replace them.
Replacement calipers are only as good as the person rebuiliding them.
I've had the one's from Auto Zone lock up on me.
X2 on the hoses.
I have had a hose fail in "Check Valve" mode (on a car thankfully)
In this mode, which was one of the early thoughts on the Bosch brake issue with Workhorse, You press the pedal and the brakes engage, you release the pedal and the hose does not let fluid flow back to the master cylinder so the brakes remain partially engaged and quickly over heat, blow the tire and otherwise mess you up.
Home is where I park it.
Kenwood TS-2000 housed in a 2005 Damon Intruder 377