I've inherited a solution of 0.5 M NaOH and 0.2 M NaBH4 in water from mid-2011. Do you have any advice about possible degradation of the borohydride?

I know it reacts upon contact with water (that's why I'd like to skip preparing it a new), but afterwards? I assume the storage conditions were 15-30°C, mostly under ambient light, but possibly some direct sun-light at times.

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