Photoshop saves the last 30 files you have opened and display them in the Recent Files list (File > Open recent) , but only the last 10 items will be available!
To set the number of items for recently opened files:
- First, you will have to open the Preferences dialog box,
- Press CTRL + K (Windows)
- Command + K (Mac)
- Click on "File Handling" on your Left
- At the bottom of the Window, in "Recent file list contains:", type: 30
- Press "OK" to finish