I apologize for bump this old thread, but I would like to share my experience in this matter, since when I was looking for good advice on this topic for myself.
The best performance by a good margin was block ice, especially if it's brought down to a lower temp in a home freezer before use. For example I just checked my freezer side of my fridge and a block of ice in there is currently at -26.2*F. The Techni-ice would start off just as cold, but is not as long lasting as block ice, but it's longer lasting than bag ice, while also being lighter weight.
Any time I pack the cooler, it's always a tradeoff between how much ice to use and how much beer will fit. If the purpose is to keep beer cold with no other source of ice for 6 days, I'd probably use 1 block of ice and a couple of Techni-ice sheets at either end of the cooler. If I only needed to keep the beer cold for 3 or 4 days, I'd probably opt for 6 - 8 sheets of Techni-ice and get a few more beers in the cooler, while also saving weight. In short,My T-I
https://coolerexp.com/best-beverage-cooler-review/ has replaced bag ice when I have no source of ice on the trip. If I'm camping in the RV, it's not a issue because I have an ice maker that puts out about 20 lbs of ice between breakfast and dinner.
My fave setup for 2-3 day trips is one cooler for food with T-I layered in it, food stays really cold, doesn't get soggy. One cooler for water and soda with T-I in it and a 3rd cooler with beer, ice cubes and rock salt to get it colder, it doesn't melt any faster.I like watching a video on YouTube on such topics, I'll leave you one of them here, I hope it will useful to someone
https://www.youtube.com/watch?v=YGT6p0anc9Q