I'm not sure if the repeat is limited to only once a week. If I remember correctly, it was set to only repeat after one full day is passed. so theoretically you could have the same daily challenge on Monday, Wednesday, Friday and Sunday.
If you swap out a challenge, this one is considered not to have been issued, so it can strike again the day after. The swap only is valid for the current day.
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I dreamt of spending a day riding a stallion. It was a nightmare.