Do you change your underwear at night? What about your bra?

Question for both genders:
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I've been wondering recently... do people change their underwear at night? Possibly into boxers, if not in boxers already?
If someone were to do this, could you switch back to the previous underwear the next day? Would it still be clean enough or, would the previous underwear considered dirty still?

Question for females (or crossdressers/transgenders)
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Do you sleep with your bra on or off? Would it matter?
If you do sleep with your bra on, do you also do the same underwear route? Do you just wear the bra straight-through the day to th night, changing it in the next day or two?
Or do you take it off when you sleep but, putting it back on the next day?
Do you change your underwear at night? What about your bra??
Do you change your underwear at night? What about your bra?
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