4 hrs is the max, regardless of lounge access or not. If the size is the only consideration (aka - there's nothing like fluids or sharp objects that can't pass TSA checkpoints), you can bring through TSA with you and gate check it (or if you'd prefer, go back landside, check in at bag drop at T-4 hrs, and reclear security). I'm sure that doesn't help much, but it's an option..