Let's start with the obvious - because C-Quad's have spars, they will break - no matter how carefully you treat the kite eventually the spars do break.
I have broken the leading edge spar a couple of times - the first time was my own fault in trying to fly in a silly wind by myself, In fact I gave up even trying to fly, but had big problems putting the kite away (nearly got the things wrapped around my head). A gust of wind suddenly caught a wing tip and simply snapped the leading edge.
The other times were, I think, just wear and tear. I get the impression that where the vertical spars attach to the leading edge does cause wearing on the leading edge spar itself, and hence becomes a weak point. At least that what it looked like to me. Anyway it did require a new leading edge spar......
I have the feeling that the C-Quad bridles aren't exactly the best quality bridles on the market. However given the low price/high performance I think this can be forgiven! I was buggying with the C-Quad 3.2 in moderately strong winds when suddenly one of the power bridle lines snapped near to the flying line attachment knot.
This of course made the kite fly very poorly until the damaged bridle was tied back on. It looks like the whole portion of damaged bridle will have to be replaced, but surprisingly the kite performs well enough with just the 'field' repair.
I'm not sure why the bridle failed - maybe there was some damage, but normally it's the point where bridles attach to the spars where damage occurs (splintering leading edges being a major culprit).
I have noticed that the little plastic connectors between the vertical spars and the leading edge spar are prone to damage. I somehow managed to break one (I think one crash too many) which caused a vertical spar to become detached from the leading edge. This promptly went straight through the sail fabric. And went through a second time in a different place when trying to fold the kite afterwards.
The connectors are actually cheap to buy (a matter of pence from a kite shop) and not too hard to fit. Just then have to repair the damage to the sail using patches.....
Apart from the sail hole (caused by the connector) there hasn't been any other problems - so far the bridle lines have been fine, nothing else appears to have stretched or broken.
The sail hole was simply patched using some Flexifoil sail repair tape as the hole was very small. Anything much larger needs to be repaired by a proper patch. I certainly don't notice the patch, and the kite behaves normally in flight.
Also be careful if flying with a broken leading edge - if the break is near a bridle line you may find that the sharp carbon edges cut through the bridle where it's knotted around the spar. In this case you either have to re-knot the bridle (making that portion of the bridle a few centimeters shorter) or replace a portion of the bridle. I know which one I prefer......