Currently each user can open up to 3 free prize boxes in a single day.
We are continuously experimenting and learning which systems are best for enabling the most amount of people to play and win. Limiting how many new prizes may be received in a given day is one aspect of this exercise.
One tip to avoid reaching your daily prize cap and running of account balance too early is to try playing lower power play levels to avoid risking all of your balance in each game. This will enable you to play even more power play games each day.
If you do ever reach your prize cap in a given day, you may continue to enjoy unlimited play in the practice arcade, where you can level up your game before returning to receive new prizes and play for big bucks the very next day!