As wolf said, they're bulky and heavy. I wouldn't rely on them 100% for that reason, but maybe one per day that you plan on being in the pack, along with a heater for each of the entrees, along with wet wipes and something like rice to for the base of your other meals, and snacks between. And a few maindays or datrex packs just in case at the 72 hour mark you realise that what you really needed was a 100 or 120 hour pack.

Just remember to strip your MREs, there is a lot of stuff you won't need. Example, break down your accessory packets- you'll only need one spoon, and the matches suck. I actually suggest the entrees and maybe some sides, and build the rest of it yourself, you'll be able to align it more to your personal taste and it might even cost less. Even if you don't pull anything, they're smaller and a bit easier to pack if you do that, IMHO.

http://www.longlifefood.com/

They have some of the best prices I've found for the entrees, and a great selection. Thier red beans and rice isn't quite jagd, but it is pretty close, and if you are stressing, the milder heat is probably better for your belly.

http://theepicenter.com/mre_military_meal_ready_to_eat.html

The prices aren't as good, but if you have a hankering for something that isn't part of the menu list any more and want to be sure it was properly stored, these are good people to try.

minimus.biz

If you are building your own accessory packs, a great resource. The only place I've ever seen where you can buy 1 (one) ketchup packet! (If you are bugging out by car, and have room, a coffee can full of things like soy sauce, mustard and so forth might be handy trade items if you find yourself in a public shelter, although some of us might think that sleeping with the storm is about on par.) They've got just about every condiment you might want in the little single serve squeezies, along with other odd single use or small package items, like rolls of toilet paper about the size of a roll of quarters.