I understand. At some point, you'll make changes to your codebase that are no longer compatible with XP. Hopefully the new feature or way of doing something justifies going that route.
I understand that pov. I also understand the pov from the other side of the fence. Take, banking systems for example. The underlying code base that runs the show is decades older than myself. The interfaces have been modernized, but, the mainframe is still it's old self. It's people still manage to support it and ensure whatever new web based 'updates' they roll out for clients/atm machines still talk to it as needed.
It just depends on what the code is doing/being used for as to you're willingness to support it for xxx amount of time. Some projects aren't so easy to port, I'm sure you've been down that road yourself.