My farm is as level as a pancake, so brakes are usually an unnecessary option. On my JD 4120 (5 of 9 tractors with a parking brake), there is a big red light of the dash, and no mistaking that the brake is set because then tractor will only move then in a real low gear and high RPM. On another little one with a parking brake (troy-built bronco), it does not work at all. In fact the only way
I can get that one to stop at all is when it is in reverse, and I engage the mower. A screwy (handy for me) safety feature that I capitalize on when storing, by backing it into its spot. That kills the motor and stops the wheels as good as a "real" brake.
Other tractors brake situations are: 1951, Ford 8n that right side still works good, but no left. I work with that by only working fields with hard right turns. There is a big difference between one brake and no brakes making that tractor still reasonably safe on hills or the road. Allis Chalmers "C" that both "original" 1941 brakes still work perfectly on. This makes that old trike an ancient "zero turn", real handy for cultivating or maneuvering in the woods while dragging logs. Farmall Cub whose brakes are completely worn, but no real need for any. I can always drop the cultivators to make it stop or hold it in position. Wheel Horse, 1980 something, 12 hp, gear, riding mower on which the parking brake still work perfectly. A second, 10 hp Wheel Horse, same year, on which the parking brake still works but the Kohler engine is pretty much shot. 1980 something JD 770 with non-working parking brake, but regular brakes still work so-so (probably because the prior owner did what you did). And lastly, an old 1951 JD "M", on which the brakes are completely worn out from many years of normal use.
From all of these, I have seen that with normal, proper use, a parking brake should last for many years. A little bit of misuse will take out or damage the tractor's brakes in short order. Obviously it is best to be careful here, especially when you have a tractor, like yours, that will operate almost normally with the brake set, and give you no clear indication that it is on. The good news is, as long as your place is fairly level, brakes are no big deal. That especially true if it is gear-drive, meaning you can always hold position by shutting down engine while in any gear.
