Might want to read his SITE clearly states the 'as is' nature and best effort of the production of these units and the very LIMITED warranty.
I've checked, there is no *very* in his limited warranty. I've bothered to search forum to clarify the issue and have found the relevant post:
https://bitcointalk.org/index.php?topic=179769.msg2780643#msg2780643Yes all boards will be tested at the factory, any defective chip will be replaced by me free of charge as part of my service.
(The chip failure rate should be low, as they are factory tested as well)
So: After the assembly at burnin's facility the boards will be tested, and if you sent him broken Avalon chip he will replace your chip with his chip free of charge.
True, that doesn't include if you fry the chip overclocking it.
Edit: My point was originally that he believes the chip failure rate will be very, very low, since he will be assembling hundreds of thousands of chips.