How long do bento ingredients keep in the fridge?

If I can think of one single question whose answer would help me be a better bentoist, it's how long bento ingredients (carrots, rice balls, veggie stir fry - anything) can be expected to sit in the fridge and still come out not only nontoxic but tasty. For instance, I stir-fried a little bok choy for bentos later this week this evening - but will it still taste good on Monday? On Thursday? Does anyone have any good guidelines?
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