The question how often it breaks : Well it depends on how hard you wheel your rig . I've been wheeling over 30 years and broke 1 axle , I do run some pretty extreme trails here In Colorado , No 2 people drive exactly alike on the trails it depends on there pucker factor, as for price to repair nothing on a jeep is cheep! also every break has different components that break , another thing it depends on what axle your talking about . Armor is always worth getting saves oil pans , tranys , transfer cases , fuel tanks ect under the belly of the jeep , I also armor the body to protect from the occasional scrape up against a rock or tree or light roll , Everyone's different on how they build their rig some are anal and some don't care .
hope this answers your questions since they were kinda vague