How long do I have to reply to a paid question?
Seven days. Answer inside that window and the tip is captured; miss it and the authorization is released and the asker is not charged.
Your tiers can promise faster
Each tier carries its own reply window, commonly 24 to 72 hours. That is your own commitment to the asker, with the 7 day limit as the backstop underneath it.
60 answers in the Nudge help centre.