If there is no play in the hubs, and no noise(usually a low rumbling or humming) from them, normally changes in tone or pitch while turning one way or the other at higher speeds... There's really zero reason to change them on a daily driver.
I've got 95k on mine, which includes several hundred autocross runs, a track day, and 40k of which was commuting on crappy roads with ridiculous spring rates and 200TW tires on 7.5in wide wheels.
They're pretty tough little cars
Fwiw our cars use the same size wheel bearing as the bigger and fatter Fiestas, and while the ST hub bearing has a different part number, all the dimensions are identical(so I'm guessing there is a difference in ABS tone rings).
As far as procedure goes, it would be pretty much exactly like a Mazda3, or any Honda really. Remove steering knuckle, press out the hub flange, which will almost for sure come out with one of the old inner races so you need to CAREFULLY cut a groove in the race then break it with a chisel to remove. Then remove snap ring, press out bearing, press in new bearing being careful you put it in correctly(ABS side inwards) and not press on the dust shield - only the outer race... Reinstall snap ring, then press hub flange back in while supporting the inner lower race so you don't push it out and screw up the new bearings in the process.
All this hopefully without mangling the dust shield