The appliance import will take roughly as long as an appliance export. On my Windows 7 machine with a 10KRPM drive, it goes pretty quick, about 10 minutes. This is way faster than installing Windows, so once you have an appliance you can create a clone in about 10 minutes. The 1st clone is about 20 minutes since there are 2 operations, export and import, but subsequent clones are only imports.
You now have a VM named "XP-LabVIEW 7.1.1", and you can create several others named "XP-LabVIEW 8.6.1", "XP-LabVIEW 2009" etc. You can also create VMs with names of specific configs for a customer like "XP-config01", etc.