Two swap questions

I have a setup where I mount swap over NFS with the following entry in 
my fstab file:
nfserver:/export/swap none swap sw,nfsmntpt=/swap

where the swap "partition" is actually a file on the server, as 
described on this page:
http://www.onlamp.com/pub/a/bsd/2003/09/25/Big_Scary_Daemons.html

This works fine if the 680 is on the network at boot time, but if it 
isn't the boot process hangs while trying to mount the swap, and 
doesn't continue until I hit ^C.

Is there a way I can the machine ignore the swap if the network isn't 
available, while automatically mounting it if the network is 
available?

Second question: I am going to set up swap on my CF card, to be 
mounted manually only when I need it. I know people say this isn't 
good for the card, but I'm going to try it anyway.

Would it be better to actually create a swap partition on the card, or 
to simply use a file? My preference is to use a file, as I will not 
have to rebuild the entire CF setup. So my question is really whether 
using a swap partition rather than a file is so much better that it is 
worth the trouble of repartitioning the CF card.

Mike