I have not been active lately on Duelbits mainly due to work reasons, but never received a 5$ bonus, so there must be other rules in place which decides who gets the bonus and who not. Would like to receive one though lol; would use to make a crazy multiple in the sportsbook.
You may have to check inbox messages in emails, exclusive messages should be claimed on private messages so maybe no special category gets bonus and many opinions just random users get exclusive promo codes, I have checked posts from @ryzaadit and he is very lucky to get more bonuses every month.