WP Cache and Memcached

I’ve just implemented memcached on my wordpress install, using a slave server and the drop-in replacement for the WP Object Cache (http://dev.wp-plugins.org/browser/memcached/trunk?rev=4548)

How do I set the memcache’s cache to expire after a certain time?

I’m having some difficulty with this since I think the default is never. I’d like to change that.

Thanks for any help.