Hello there! In my opinion you definitely need more than 4 days in the Antarctic Peninsula to make it worth it. As you will travel all the way there and if you don't pick the "fly-in fly-out" option you have 3 days crossing the Drake passage approximately in each direction, so to make it worthwhile I recommend more time. A week in the peninsula should be amazing, especially if you can do different activities like camping, kayaking, hiking, visiting different bases, etc.