The first time I updated my iLiad via iDS took a long time. I watched it for 3 hours, downloading, re-booting, downloading, then I left it to finish overnight.
Updates depend on the size of the update and the speed of your connection. Make sure you have plenty of charge in your iLiad before you attempt your iDS connection.
Can you do a generic iDS update? see
https://www.mobileread.com/forums/sho....php?t=41281#4