Hi Jessica.

I also date the bags with a Sharpie like the lady who commented below you. As for how long, I've usually used them up before the 4 month mark and they were fine up to that point.

A good rule of thumb though, is to take note of the cubes when you start noticing a little crystalizing around the edges or in the case of the tomato paste, a little bit of cracking. At the first sign of this, you can probably still salvage them for one recipe for another. For example, one time my tomato paste cubes sat there for longer than normal due to a crazy few months with family and business stuff. When I noticed the edges getting a bit cracked / dried, I planned a thick spaghetti sauce and thinned out the paste cubes with puree and clam juice for a red clam sauce. It worked fine.

These really are a huge help and time saver Jessica, if you can find the time to do them. You just reach in and grab a couple cubes for whatever you happen to be doing. No opening the can and scrounging around with a spoon to get every little bit out. Just quick and easy. Good luck, and keep me posted.