During an editing session, Peak maintains an internal list of all your edits. If you find at some point that you're not achieving the results you were hoping for, it's not necessary to start all over again. Peak doesn't apply the edits to the audio file until you're satisfied, so you can always go back to any specific edit. Under the Edit Menu, select the Edits command. This opens up a window where each edit is listed. You can click on any of these to take you back to a specific edit or revert back to the unedited audio. There's no practical limit to the number of edits you can make, as long as you don't exceed the available RAM in your Mac. But since most edits are just a list of commands, each one only uses a small amount of memory. Thus it's not unreasonable to expect an unlimited number of edits that can be undone at will. You can also go back to any individual edit to hear the result.