AFS will cache.
Caching NFS (solaris, irix) will cache.
A local objet target will speed things up.
A local /usr/pkg/distfiles will speed things up.
A local disk (duh) will speed things up.  Even if it's
temporarily placed there.  With no idea what platform
you're talking about... at this point, drives < 1&2GB are
usually free to come buy (both IDE, laptop and SCSI).

My little soekris appliance has a 2GB(!) drive from a Mac
WallSt G3 laptop (the laptop got something of useful size).

Tossing a 2GB+ drive onto a build machine isn't terribly
burdensome - for my machines.  If I can't, then patience or
something else to do is fine (I just watched my P/500 monitor
box at work spend around 8 hrs to build all of gnome).

Quoting Michal Pasternak (michal@pasternak.w.lub.pl):
> Let's look at situation like building mozilla with pkgsrc when everything
> (/usr/pkgsrc, /usr/pkgsrc/distfiles, WRKOBJDIR) is mounted via NFS:
> 
> 	- checksum:
> 	  - fetch whole mozilla source tarball via NFS
> 	  - calculate checksum
> 	  
> 	- extract:
> 	  - fetch whole mozilla source tarball (again) via NFS
> 	  - extract every piece of data back via NFS (size of tarball
> 	    multipled by at least one point something)
> 
> This can take some amounts of time. While doing one package, time doesn't
> matters as much, as when bulk building.
> 
> Do you have any ideas how could I get around this?