Archiving / exporting tickets

I’m wondering what people out there do when they finish a project and want to
move all related tickets to an archive (perhaps a second RT instance)?

I’ve set up RT with a custom field of ‘project’. When a project comes to an
end, I’d like to be able to export all tickets with that project value (and
then remove them from the RT database)

If this isn’t possible, might it at least be possible to ‘hide’ all tickets
with that project value, so they don’t come up in any searches?