Yes, I know, they always seem to take forever. I have two identical IP6000s on the same network, same settings apparent through the web interface. One boots in a few minutes, the other takes two hours.

Interestingly enough the one that boots quicker is on the "wrong" on the VLAN, and the one that takes longer is on the phone's VLAN.

the phone on the voice VLAN may have LLDP/CDP enabled and is getting the wrong advertisements - you can check in the Network>VLAN settings.