RO Membrane Question!

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Hey Everyone! Just a quick question about ro membranes. The town I live in was under a do not drink water advisory for the last 3 months due to extemely high sulphate and sodium content. Ive been using purchased ro water for the last 3 months because my home system wasnt big enough to get rid of all of it (just a 3 stage system) The lowest i could get it to output was about 60ppm. Anyway the advisory was lifted last week and I would like to start using my home system again. My question is to how long the membrane and prefilter would last with water sitting in it. I didnt empty the housing or anything when i stopped using it. Can i just run a bunch of water through and continue using it again. Or should i replace the membrane and pre-filter. The membrane doesnt actually have that much use to it maybe 4 months total before i stoped using it! Any feedback would be much appreciated!