Once your hosting credit reaches zero, your site will then turn over to "This Page is suspended" message page, until you bring your hosting credits to positive value. I believe it's 4 then the site becomes active again. During the suspended time, you won't be able to upload via FTP or cPanel.Yes, it is strongly encouraged that you stack up your hosting credits when you know you'll be away for a long periods of time. Perhaps you should think about the paid hosting? I don't know. It’s not that expensive.