Alright, I have researched water storage a bit on the internet... so I'll share what i learned:
Sealed water supposidly can be OK forever (there is a date on the water containers, I called the water people -- I am thinking it was Crystal Gyeser -- and they said that he water is guaranteed "fresh" up til' that time, but it is consumable for a great many more years). The only problem is that it loses it's taste (my guess is that it gets the plastic taste from the water bottle it's been in -- but I have heard it is due to a loss of aeration so if you poured the water back and forth from a couple of containers and let it sit for a bit it'd taste better). I have some sealed containers that are about 5 years old. Now that I have my full storage of 24 of them, I am going to rotate them buying 6 or so new ones a year and throwing the oldest out (and using their water to water my plants). You can store water in pop bottles and old water bottles, but you do have to switch those out, becuase they're not sealed. I'm not sure how often you have to switch them, I'm guessing yearly.
As far as my water barrel in the back yard, our friends the Yuens were kind enough to give us the one we have. I think it holds around 50 gallons, and I guess they used to be used to store olives, but were then cleaned and sterilized for water use. I switch the water every six months to a year. When I pull the lid off, there is some crystalization on both the lid and the top of the water, but I have never seen anything growing inside. I keep the barrel in the backyard by our shed. It's in the shade but I do have to clean-off the top when I open it (becuase it has all sorts of nastiness from being outside on top of it). I got the pump from a friend, but I have heard they're pretty easy to procure. I am guessing, if you're LDS, if you talked to your ward or stake emergency preparedness coordinator, they could point you in the right direction to get both the pump and a big barrell if you're interested. I did talk to our local watermaster and he said that I didn't need to add bleach to the water that went in my barrel because the city has chlorinated water. I would check with your local people. If anyone else gets a different answer I would love to know. However, bleach and myself don't particularly mix... I've ruined quite a few pairs of pants due to bleach -- it's not something I want to talk aobut...
I am also wanting to get some water purification tablets to put in our 72 hour kit in our car... our ward preparedness coordinator also mentioned we might want to get some cofee filters to send any water that is visibly contaiminated through.
I have also considered on putting some crystal light also in our 72 hour kits because I am guessing any water that has been "fixed" in this particular way isn't gonna taste so hot. And we all know that I'm gonna want to be happy in an emergency.
Anyway, those are my thoughts and what I've learned, take it for what it's worth.