Don't worry about keep saving your document. Changes on your presentations are saved automatically as you work, just check the notification displayed on the top right corner of your screen.
All you need is love and a steady connection, of course. Whenever there's trouble to save updates, you'll also be notified and have the chance to retry saving.
On your Dashboard, you can check the time since the last update on each presentation. Just click on it to see its details and take actions like Edit, Present and more.