Missing NFS shares slowing down boot ?

I am wondering why my desktop is taking 5 minutes or more to boot up. There are a couple of (i.e. 4) network shares, 3 of which are not always available at boot-up, so I'm guessing there must be a NFS share time-out somewhere that is set rather high. Does anyone know where I can go to tweak it? Or are there any other suggestions where the time is going?

I am running Opensuse 12.3 (64 bit) with Gnome.

Cheers
hn