If you want them to last longer, avoid rails. If you dont wanna do that, flip the skis so you have the left ski on your right foot. Edge cracks usually happen in the place where you land on the rail, switching the skis might get you a few more days before more edge cracks appear.
If the cracking gets really bad, maybe some epoxy to keep water from getting into the ski. If it pulls out, epoxy over the gap after cleaning the area, or if you wanna spend the cash, take it into a shop and see what they can do. It is not cheap, most charge by the inch.
And from the standpoint of a consumer, yeah, its a rough deal to have this happen. I hope he does get a warranty, but from the standpoint of a company, you have to have a firm policy, and you have to be able to understand that. Otherwise, wheres the line? What constitutes a grace period? 30 days, but not 31? What kinda days anyways, days skied? Days past purchase date? Number of rails you've hit?
Really, the only solution is to either find a way to make skis so cheap that companies can afford to replace them willy-nilly (I hear theres a wakeboard company that warranties any sorta damage because their manufacturing costs are so low, you just have to send a video of you destroying your old board), or for someone to set up some sorta ski insurance plan... both of which dont sound too appetizing...