Hmm, that's odd. My javascript may be a bit off, but it's supposed to not expire for a year. This is the bit of javascript that controls that:

Code
expires = 365 * 60 * 60 * 24;
var expires_date = new Date( today.getTime() + (expires) );
document.cookie = id + "=" +escape( value ) + ";expires=" + expires_date.toGMTString()  + ";path=/";

I'll need to tinker with that and see if maybe I'm doing something wrong.