Lee242. I use an old (plastic) vinegar bottle to store my master batched lye solution. I've rinsed it well with tap water then a final rinse with distilled water. I have a 50% solution (1:1) that I dilute and a 33.333% (2:1) solution that I don't dilute. The reason I have two (if you're wondering, because it is kind of odd) is because I always soap at 33.333% so I master batch. But, occasionally I like to use an alternative as part of the liquid. I can't do that if I use the master batched (33.333%) solution and I hate mixing solution each time. So, I have the 50% solution and I use the alternative liquid as the extra. It gets a bit tricky if I want to use vinegar as the alternative liquid, but I can actually manage the math. I need to use two sheets of paper and have to take my shoes off, but I can manage it. (TOMH, that was for your benefit. :wink
As far as NaOH going bad if left in solid form (there are flakes as well as crystals), I don't think so. I don't think it goes "bad" per se. (like oils or meat). However, if it is exposed to the air, it will suck any moisture out of the air and form lumps, which in turn will make it less effective (don't know the scientific term). So, you definitely want to make sure it is in a tightly sealed container. kchaystack told us about gamma lids and damp rid. I think several of us are using his set up now. (I know I am. My lid is bright orange!) http://www.soapmakingforum.com/showthread.php?t=59316
If you keep granular NaOH in a tightly closed container in a low humidity environment, it will last a long time. Problem is you need to be careful about keeping fresh air away from stored NaOH. Air contains carbon dioxide and water vapor and NaOH will quickly react with both. That lowers its purity.
I am happy using a storage method that KChaystack suggested --
Buy a polyethylene 5 gallon bucket. Either use the lid that comes with the pail -- this is the kind of lid you have to pry off -- or buy a separate "gamma" lid that can be screwed on and off the pail. Gamma lids are available online and in large building supply stores in the US (Menards, Home Depot, Lowes, etc.)
Buy a small bag of NON-clumping kitty litter or buy a desiccant pack. Desiccant packs usually contain silica gel or calcium chloride or calcium sulfate. Any will work fine. Damp Rid is a desiccant product you can often find in Walmart and hardware stores.
I use a desiccant meant for gun safes that has an indicator that tells when the desiccant needs to be recharged. It's fancier than really needed, but I had it on hand.
If using kitty litter, put 2-3 inches of litter in the bottom of the pail. Put your containers of NaOH in the bucket on top of the litter. If using desiccant, put the NaOH containers in the bucket. Add the desiccant pack near the top of the bucket, so you can check it from time to time to see if it's still working. Put the lid on so the bucket is air tight and keep the lid on as much as possible. When you need to use NaOH, be sure to replace the container back in the bucket right after you're done using it.
Important -- Keep the NaOH in its own containers and those containers go in the bucket. Don't put the loose NaOH flakes/granules directly in the bucket. A few folks have gotten confused on that point.