Do you have anything in your CMDB (Class, Tag, Naming Convention, etc.) that identifies these devices as ephemeral (short lived) in nature? If so, I would leverage that to auto-close or exclude them on the ServiceNow end. We do something similar for our virtual desktops that are created/destroyed daily. Make sure you still bring in and action anything persistant and/or the image/template server so you can action those and avoid creating vulnerable devices even if they are temporary.
