Let's assume, for the sake of this question that someone likes to change the domain of it's site once a year or 2... Why? From whatever reason, let's just assume that...
The only elegant solution for doing so without risking the SERs would be, I think:
- Keep renewing the first domain.
- Making a Wildcard Redirect via .htaccess from the old domain (or domains) to the new one. Each redirect would be valid of course, only if the alias wasn't changed by itself.
- Informing the Search Engines for each change?
What do you think?