Today is exactly a year since I've began working continuously daily on 1337chess PLUS or PRO opening book series. Engine chess and making opening books has been a hobby of mine since 2005 and this is the most tedious and the longest that has been developed so far.
Years of CPU time has been spent, over a thousand book versions and a couple of terabytes worth of opening books tested. Thanks for all your support, we hope to continue making better opening books in the future. :-)