In terms of sustainability - remember, Chris has been an FPGA developer for well over a decade long before bitcoin was ever even around. That would mean that he already had the relationships with the chip manufacturers, and the foundries, and would already have been familiar with their business practices. That alone would put him light years ahead of the competition.
It makes you wonder how many PHD engineer's are out there designing ASIC's and FPGA's for companies like Nokia and Intel and stuff who have just never thought about putting their skillset to work in Crypto. :p
We have no idea the specs for either the FPGA boards or ASIC chips that Chris is using - but it's not unrealistic to assume that he could be having a foundry in China manufacturing them for him in bulk. (In fact, he's been to China twice on trips to his foundry). Remember, he's not just a college kid who tried learning about building ASIC chips at school one day and then wanted to start building miners. :p
If you join #LTCGEAR on freenode, they've done a ton more background research into him and his setup. Feel free to PM me for a few of the details, I don't feel like sharing them all on a forum because to the best of my knowledge they haven't posted a bunch of his info online.