try to:
first delete the vendor.xml
then run the update directly from application loader( that is from the ProgramFile/CommonFiles/RIM/etc. just look it there)
the time it takes depends on the pre-installed applications with the new OS (you can delete some just google on the net for guides on how to make BB pearl Faster)
also the time it takes to delete all installed apps affects somehow
mostly, after OS instal, what takes longer is loading the backup especially if the backup contains too much data and/or have too many applications with it like game infos/saves/etc/ somehow before installing new OS for fresher and faster install, choose delete all apps in the advance tab.
you may also want to try using Crackmem for safer /easier way on eliminating unnecessary pre installed applications.
heres Crackmem
http://bbsgame.mobi/thread-4362-1-1.html
hope this helps