Caching question for large (ish) file

[brad at ftwentertainment.com]

Hello Everyone! First time E-mailer with a small question I hope  
someone could answer for me.

I've searched through google for my answers but i haven't found  
anything that tells me what i'm doing wrong...

So I have a test setup that has a Dynamic node and an edge node. The  
single point CDN is up and working (thanks to a ton of help my a buddy  
of mine). But one issue i've seen is that in our tests, even after  
specifying a month for a cache time, the server still seems to delete  
the cache when i come back around 24 hours later.

The goal of the long cache time is that I'd like to create a CDN  
platform that I could let users stream video files that are >100MB...  
The video files would obviously not be changing within a year (let  
alone a month).. So one of my thoughts is that the size of the files  
are the reason for the deletion of the Cached content..

My apologies for any stupid questions, i've been working on this for  
the last few months and finally just decided to email the list to see  
if anyone would be able to help..

The configuration of the edge node for the proxy cache for the server  
block is as follow..
location / {
       proxy_pass http://static.mysite.com;
       proxy_cache site-cdn;
       proxy_cache_valid  200 302 301 any 365d;
       proxy_cache_use_stale updating;
       proxy_temp_path      /var/www/cdn/site/temp;
       proxy_buffering on;
     }

Thank you for any help! I truly appreciate it!

-Brad