
Kman and CaptBob posted some very helpful comments in a thread about two years ago:
viewtopic.php?f=19&t=2459&p=27936
Overview:
Here's a closeup of the raw opened Mainstay, Millennium, and Datrex (left to right):

That's also the reverse order of my purely subjective preference.

To me, the big advantage of lifeboat rations is that you can toss some in your car, and regardless of whether it's summer in Texas or winter in Alaska, this stuff will still be useable five years later. No other "specialty" emergency ration is that versatile.


Early this year, I experimented with them about once per week over a two month period.
I found I was ok with up to about half my calories per day from them, but my body didn't feel right if I ate more than that. That was probably part psychological, and part genuine nutritional deficiencies (protein in particular).
The worst day, I had planned to do 100% lifeboats, but after 1000 calories worth of Datrex and Millennium bars was feeling very poorly (partly influenced by some prolonged unexpected car & motorcycle noise), and decided to have one modest hot (microwave) meal. Later that evening, I had the strong feeling that I was salt deprived, so I made a packet of powdered soup, then had a banana, for a total of 1415 calories for the day. I may not have been drinking enough water that day.
I need to do some more experiments some time when I don't have to be at my peak, mentally, and can push things more.

Mainstay:
I like lemon, but the Mainstays were cloyingly sweet, and the only one of the three that I did not like. I was able to eat it, in small quantities, but ate less than my planned amount each time I had scheduled it.
Mainstays come in one single brick with light scoring marks. They're definitely "fussier" to deploy than the other two I sampled.
In most taste polls, they come out first, but frequently have voters who strongly dislike them.
I strongly recommend trying a small size, before stocking up.

I have a theory that these may be more popular with children. I welcome experimentation by the forum members!

Millennium:
The Millennium "energy bars" were a pleasant surprise.
First, some pictures...
beside a can of soda for size reference:


close up of raw bar:

nutrition and ingredients:

They're the most expensive of the three, but not by a huge amount. The 400 calorie package is the most flexible, and multiple flavors is a nice way to reduce food fatigue, though I found the texture and base taste were more dominant than the mild flavoring. These are the most dense, but they're thinner than the Mainstays, so they're easily manageable. The "notch" makes opening them easy.
One significant downside is that they were the only ones containing trans fat. Not a big issue in a "real" survival situation, but a factor in stocking them for routine field use. I'm still planning to carry at least one in my birdwatching field kit.

Datrex:
My favorite was definitely Datrex.
Each brick contains individually wrapped 200 calorie portions, which makes these very flexible. The taste is the most bland, but in a good way. There is a slight aftertaste that has been described as "oily" - I don't think that's quite what it is, and it wasn't "bad", just be aware of that. These crumble very easily. When you open them, there is a very strong smell of coconut, but the taste is much milder. If you like coconut, the smell is nice, psychologically (IMO).
Of them all, I was easily able to eat these as a snack, both during my planned days, and on other days. Ever since I bought a 4-pack of 2400s a year ago, I've kept a few loose ones in my car gear, as a cheap & easy emergency snack.
Bottomline:
I think Lifeboat rations are an excellent addition to a layered car emergency kit.
The heat range of these is outstanding, with no real competition. Having some of these all but guarantees you'll have something edible, even if you miss multiple rotations of more heat-fragile food. Particularly for you Southerners, these rock.

They are not as psychologically & nutritionally satisfying as MREs or freeze dried, or other "real" foods, however they're a great way to "strech" limited real food.
They're the most cost efficient of all the specialty car emergency foods (assuming you don't pay a crazy price for them).
Next:
I'll post up some vendor info, and more pictures (particularly of Datrex and Mainstay) including nutrition information.
I'd like to try the other varieties out there, so I welcome frugal vendor info.
