Prepared Minimalist

Question: Are MREs and emergency buckets any good and how long do they last?

Answer: Most buckets claim that they last for ten to twenty five years as claimed. 
While buying buckets like this might be quicker and easier, I wouldn't recommend this for a few reasons... 

Most likely you'd be eating that food bucket during an emergency, and changing your diet in a stressful time does not go well. 
1. MRE's and rations can cause constipation at a high rate if not stomach pains as well. Many bars are also extremely hard and will threaten your teeth when biting into certain companies.
2. You or your family will be less likely to eat or be able to eat a pre package dinner. Some may outright refuse to eat it, or worse...that there is a chance you are allergic to an ingredient.

Solution: Now a different approach to this would be to start your own extra panty. You could get a good two good years of food this way and with sales and coupons during the year can be a bit cheaper way. Best of all you know that your family will eat this food! 

Step1: You need space to do this which has no sunlight, no moisture, which is 40-60 degrees or constant temperature, and is off concrete or dirt surfaces. This could be a garage, a closet, underneath staircases, or in basement. 
Step2: Once you have the area, build shelving which you could do yourself. Measure the size of a 5 gallon bucket for flour lets say, and then the size of a cereal box, and work your way up. It will basically be your mini supermarket. Make sure it's in an easy access spot to ROTATE! This will save on wasting food.
Step3: Time to stock! Basically each time you go to the grocery store... buy a couple extra stuff to keep your own house inventory. Start with dry ingredients / staples like oatmeal and flour and then spices, honey, raisins and such. Like I said only buy what you are eating now a days though. You won't want to get stuck with the food...
Step4: You could add seeds on this list if you want to grow which would extend the 2 years if need be.

TIP1 on buying: I have in the past worked in a supermarket and must warn you on their store sales. Normally a manager special means the date of expiration will be coming soon. Buy the furthest sell by date possible!
TIP2: The dates are sell by dates. Most items can be used even a bit after the date if not many months past. Frozen meat is 6 months after the date but don't rely on a freezer... A recent discovery notes that this DOES NOT apply to bakery box mixes like cakes or cupcakes. If it's over the date chuck it out. The study showed a bacteria starts growing that causes lung problems. I am unsure how much over the date.