Oh Noes!

I've been parking a domain name for a friend/client of mine on my hosting provider (Dreamhost, FWIW) for a while, and they eventually asked me to redirect their domain to a 3rd party website which is currently featuring some relevant promotional content. Once this period ends, we will probably go ahead and set up a proper website for the domain on my hosting account. I used Dreamhost's "redirect" hosting option in their domain configuration panel, not realizing that it would implement a 301 Permanent redirect, or what the implications were.

Now it seems that for any client that has visited the site anytime recently, the 301 redirect is still cached/in effect, although I have changed the domain settings back to regular Dreamhost full site hosting. It seems that the only thing that can be done is to wait out the TTL/cache expiration for the redirect. I have no idea how long that might be, so I'm wondering if there is any good way to cache-bust the redirect or otherwise undo its long-term effects. I put a simple html meta refresh in the domain folder to replace the 301 to keep the intended functionality in place, but I'm still not able to access the domain's other content normally, even via FTP, etc.

Isn't there anything I can do? Otherwise, how long does it take for a cached redirect to expire? It's gonna be a bummer if it's really permanent.