That's a good question. If the jars are and stay completely sterile, and the substrate doesn't dry out, then you should be okay. However, if you are not 100% sterile, or the substrate is too dry, you could have problems.

My suggestion is to redo your substrate when you get ready to innoculate, because substrate preparation is cheap.

~loathe~

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The girl he had dragged along to the pub with him had grown to loathe him dearly over the last hour, and it would probably have been a great satisfaction to her to know that in a minute and a half or so he would suddenly evaporate into a whiff of hydrogen, ozone, and carbon monoxide. However, when the moment came she would be too busy evaporating herself to notice it.

-Douglas Adams, The Hitchhiker's Guide to the Galaxy

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what's that you ask, the things I've seen?
angels cry & devils sing