The idea of having a few legendary items is interesting. But neither a fixed limit nor total item immortality will work. As has been said: That is exactly what the system is designed to prevent: Hoarding.
However, I have updated the code so that some items (big random factor) will over time become more resilient. Give it time, several months at least, and you will start to see a low number of legendary items that last for longer before they need repairs, but won't last forever.
