I own a few KSC G18C's, and haven't had one break yet. I find with proper maintenance, standard use and semi-auto use they work fine. You don't HAVE to use them on full-auto all the time. There are also a lot of replacement parts available.
So while I think all of the above are great ideas, I also endorse the KSC G18C. Loads of fun in full auto, and works great in semi.