I get a good solid 5-6 days out of my COLEMAN 5-day COOLER but my trick is to start out with SOLID ICE in the bottom of it. We will freeze up several milk containers filled with water before the trip Then fill up with cubed ice as we go into town etc...

We try not to open the big ice chest unless really necessary - That helps big time...
We also use a sealed plastic box in the top of it to store food etc in.
Two weeks with 90% ice still frozen sounds like a pipe dream to me but who knows what can happen these days haha...
Roy Ken