Hi Jastmo, ad elcome to the vista forums
Although it would be technically possible to create one restore image and use for re-install in the event of total failure I would advise against it.
You would possibly have have issues with licensing, unless the restore options prompted for a licence code with the re-install process, this is possible but unlikely with my experience with OEM installs.
Although the two laptops are identical models there is a slight chance of them having minor variations. With the cost of DVD media these days it would be best, to create individual recovery images, it may be worthwhile to mark the disks with the serial number of the actual laptop they relate to.
The recovery process would normally default to DVD media but I believe there is an option to create to an external hard disk so that option is valid. My policy with similar situations, (dealing with anything upto 20 machines at a time), is to create disk images and store them away plus create images to a network drive which is used for normal rebuilds.
hope this helps