I really like the UI you made. And the ability to change the number of days to keep posts is really cool too. Are you doing any checking for duplicate posts between sites?
I wouldn't mind having a side tray or list of temporary bookmarks that I could easily add to, restore from, or remove. Then I would have 3 or 4 active tabs and about 15 inactive tabs and could swap between them easily.
I know it is possible with shift + cmd + D, as one commenter pointed out, to bookmark all tabs temporarily but that would get cumbersome if you were constantly changing out tabs.