How long will it keep?

So I made a 3L starter of WY3724, I decanted off and ened up with about 8 ounces of slurry, probbably could ahve decanted more but I didn’t.  I poured two small mason jars 4 ounces each and put in the fridge with todyas date.  How long will they keep?  I’m gonna do another starter with WY1272 (I think thats what it is wihtout looking).  I want to build a little bit of a bank.  I know its not long term stuff that I’m doing… I haven’t got thert far yet.

That will last up to 6 months, if you plan on using it any longer than a week from now, you will have to make another starter to wake up the yeasties

What is best means to store - sealed or unsealed container - foil on a mason jar, a sealed with a lid?  I’d like to keep for a month in the refrigerator.