Tandems can end in two different ways:
🤎 Congratulations! You've fed and evolved your 4 pets! You've reached the final stage and claimed all your rewards as well as the grand prize! Your pets now appear in the Tandems tab, their progress is marked as ‘Completed’, and you can no longer collect food during the game. Note that any remaining food is lost.
🤎 The Tandem event is over! As soon as a Tandems event starts, a countdown timer displays the time you have left to play, collect food, and feed your pets. Tandems generally last 7 days. Once the deadline has passed, your progress and remaining food disappear. 
But don't worry, in both cases you'll receive a reminder to collect any unclaimed rewards before the Tandems end, and new Tandems are regularly organised to keep the fun going!

For more details about our various features, you can browse our FAQs and, of course, if you would like more information on this subject, we invite you to contact our Customer Service by clicking on the Settings tab (with the 3 lines) at the top right of your home screen, then on Help. To open a conversation, you can either click on the bubble 💬 in the top right corner or click on ‘Chat with us’ at the bottom of the page.
We hope you have fun playing!