How many items are included in the RSS feeds?

I like the RSS feeds because I'm interested in seeing ALL of the photos that are being added to the site, but I suspect that unless I have a fairly frequent refresh on the RSS feed, I might be missing some.

Looking at the raw RSS XML I suspect that the RSS feeds show the last 30 photos.

The RSS feed shows last 12 photos uploaded. Usually it's refreshed every 30 minutes (depending on reader software), so if many photos were uploaded in a short time period, the RSS feed will miss most of them.

Yes, you can overome this issue by setting the refresh time in your RSS client software very short, say 5 minutes.