I don't see any point...
in using XP mode under Win7. Once the support for XP runs out, I will simply use a PC with no Internet connectivity to run any applications that are needed, until they get replaced by something newer, which usually happens with hardware upgrades or replacements.
Virtualization may be the mode of week after next, but I prefer to dual or multi-boot. From my POV its easier to reboot, than to start up a virtual machine.