I have a Coleman Extreme cooler that I can put 2 bags of ice with food/drinks in and there will still be ice 4 days later. It has more insulation which means there's a little less space for stuff inside, but the benefits outweigh the negatives. Usually when I load it, the loose ice refreezes into a solid hunk (along with everything in it) the first day.
A recent example is on Saturday I filled the cooler with soda, beer, food and 2 bags of ice in the morning. When we got to Ruidoso around noon, I placed the cooler on the back porch of the condo we were staying in. When I tried to get the food out that needed to go in the refrigerator, I had to break up the block of ice that had formed. The cooler then lived on that back porch for the next 48 hours, in the sun for part of the day. We came home and I emptied the cooler on Monday at 8 PM and there was still about a half a bag of ice left in it.
If you'll have access to ice every ~4-5 days, the extreme cooler seems like the simplest solution.
Wrapping a blanket or two around a cooler extends the ice a very long time as I've found out. Heck, I even wrap my Engel with blankets during super hot days!
Covering the cooler is a grand idea. Historically I've used a Coleman stainless cooler and we always had a sleeping bag draped over it with an ensolite pad underneath. It really helped maintain "ice integrity." I do cover my Engel too, but I need to be careful not to block the vents. It needs to breath.
Just did a trip in my '63 Bus. Went to Caprock Canyons state park in Texas. Met some good friends from OK and MO for some hiking and good times.
Knowing I was going to be out in 100 degree heat for 4 -5 days,
I bought a block of dry ice for the cooler. I put the block of dry ice in the bottom of my modern Coleman Extreme cooler, and dumped a half sack of store-bought ice and several large chunks of solid ice from my freezer on top of it, and all the food/beer I could fit. I kept the cooler wrapped in moving blankets and out of the sun.
All the ice in bottom of the cooler froze into a large mass of ice which did not start melting until the dry ice was gone about 3.5 days into the trip. I still had my original ice after my friends had been buying ice daily.
On the way home I bought one bag of ice to throw in on top of the mass of ice that was slowly melting in the bottom of the cooler. And all that ice lasted a couple days more after getting home.
So I got almost a whole week out of a $9 block of dry ice, chunks of block ice from my freezer, and about a bag and half of store-bought ice.
I'll tell you, after our week in Moab back in June, I was sold on the ARB/Engel. I will be making purchase of one for the 60 for those trips. The hassle of a ice chest isn't worth it to me. The Coleman Extreme is nice, but having to not worry about ice... Priceless.
All comes down to price sensitivity and intended use.
Coleman is more flexible because you can use it anywhere regardless of a power source (houseboat trip, picnic at the park etc.) and don't have to be monitoring battery health.
ARB gives you "infinite" cold, no soggy hotdog buns, and no need to schedule ice picks-ups. But it costs 6 times the Coleman.
Thanks for the comments. My dog-show buddy bought the fridge, almost as I was typing. Did show links to Engle/ARB etc, but the initial cost was off-putting.
Do have a marine-grade white cooler (Mudbay'd, natch), and some other varieties. I like the dry ice idea, might have to try that. For now prolly going w/'spare' ice in an Igloo, so's the melted water doesn't go to waste. My fave trick is freezing tea/powerade etc in a lexan nalgene: keeps stuff cold and makes for a nice treat once thawed.
REI carries a stainless cooler, so that might be an option if my system don't work out. Also do like the Ensolite pad idea, now I just hafta figure out where I stashed 'em. They are also great as a bottom layer in dog beds, minimizes the 'gotta get it just right' shuffle.
from my grandfather. it's old and better than anything I've bought since...
They are also great as a bottom layer in dog beds, minimizes the 'gotta get it just right' shuffle. 
