You can join Live Duets for free a total of 5 times per day. It does not matter if you joined 5 Live Duets within 1 Stream or 1 Live Duet in 5 different Streams.
If you wish to use that feature more than 5 times a day, we have a paid feature for that. You can purchase additional Live Duet “Joins” through Tokens (you can purchase Tokens at the store).