One thing people have to remember is that Detuning your edges underfoot (not from tip to tail, just underfoot) properly BEFORE riding and rails and boxes can help prevent edge damage and cracks. If your edge is rounded underfoot it'll roll over the rail better and not chip away. If you ski A LOT of rails then I HIGHLY suggest detuning your skis before hitting any rails - I ALWAYS do.
Here's what I do... Step 1) Gummy Stone tip to tail on all 4 edges
Step 2) Metal File underfoot only (from the tip of the nose piece to the back of the heel piece), I go in a rocking motion along the edge so it rounds out the edge, no just put a bevel on it.
Step 3) Back to the Gummy Stone, tip to tail again.
This is what I do (and it's basically what is described in the video I posted from 4FRNT), and I have NEVER had an edge crack and I live on the east coast and ski about 97% park and do tons of rails every season. (If you DON'T ski rails A LOT it's not really necessary, but if you do I really suggest a detune).