We usually take 2 coolers. We will keep the meats and such in the 12v. Igloo and the other stuff that needs to keep cool in another. A couple gallon Ziploc freezer bags filled with water and turned into ice are placed over frozen meat in the bottom of the cooler then we just dump the water after it melts. It helps keep the meat semi-frozen for several days.
The regular cooler usually gets some water bottles frozen. It may get a fresh bag or 2 of ice over a week when it can be had. Nothing is kept in there that has to be kept really cold though.
I make Ziploc bags for SC Johnson. Do not substitute storage bags for freezer bags. The storage bags are almost half the mil thickness of the freezer bags. If you worry about the bags having a leak, simply fill the sink with water, blow some air into the bag and dunk it in and apply just a litle force to the bag with your hand. There really shouldn't be any bubbles but if there some small ones, don't worry it is an exiting force and will work fine. If you are going to put a liquid in the bag, you can do the opposite too. The part up by the zipper is where it will leak if it is going to about 99.9% of the time.
Do not even think about using anyone's zippered sandwich bag to store anything you want to stay dry in. I think they attract water into them sometimes.:sombrero:
I am not a big fan of the new Evolve line of "green" bags either. They are just thin versions of the real thing (plus the thin plastic makes them a PITA to make!).
Ziploc makes some plastic reuseable/stackable containers that work quite well too. There are even some with thread-on tops. I like the 5x5 square ones that keep my sandwiches from getting crushed.
One more plug. These bags are awesome for sleeping bags, blankets and pillows. You can kinda suck the air out of them to compress them some too.
http://www.ziploc.com/Products/Pages/ProductsHome.aspx?browseBy=Oversize&browseByCat=NonFoodStorage
We have been the Igloo for @ 5 years now and it has worked pretty good. I think we will be stepping up to a Whynter, ARB or Engel next year though.