Gmail on Safari 7 slows down after 10 minutes

I have been using Safari 7 for Mavericks since Mavericks was in beta. For every version since then, Gmail after being open and being used, any time after 10 minutes, begins to slow down and become unusable. I begin to type and I get the "beach ball" and then 5 or 6 second later what I typed will catch up with me. I can go to another open tab in my browser and other content behaves just fine. As soon as I close/reopen Safari, the problem disappears - then after 10-15 minutes of usage of Gmail it begins all over again.

I have re-installed the OS many times (for other reasons), and started Safari out clean with no plugins or extensions and the problem persists. Of course this problem does not come up on Chrome. Any idea's?