Fiber-optic tubes are breakable, so keeping spares is definitely a good idea. But if the fiber optic rods are installed so they have absolutely no movement, then they generally last quite a long time. If the rods break too soon, it is often because the rod was able to move a tiny little bit during recoil.

You can use heat to melt the ends of the rod and get it solidly locked in place. There are a bunch of videos on youtube which show different versions of this procedure.

Here is a video from 10-8 Performance which shows the approximate method I have used.