I don't think it would be feasible to maintain a fully functional copy of a dynamically generated page at the old URL for any length of time. That's just a reci

I don't think it would be feasible to maintain a fully functional copy of a dynamically generated page at the old URL for any length of time. That's just a recipe for security nightmare, not to mention the SEO penalty for duplicate content. 301/308 redirects, on the other hand, can be maintained more or less indefinitely as long as you keep around a mapping of old URLs to new URLs. If you need to change your URLs again, you just add more entries to the mapping database. Make your 404 handler look up this database first. One thing you can't do, though, is repurposing an existing URL. Hence the versioning. :)