There are now 40 possible levels for your Hog to reach, and each time you level up you gain a one-time bonus of spins (or coins at the higher levels). After level 40, levels continue to be added.
Each week you submit a qualifying receipt, you'll earn one XP and are one week closer to your next level. The higher the level, the more weeks it takes, but the fatter the one-time bonus! The benefits don't stop there though -- as you reach certain higher levels, your reward for completing your monthly challenges increases as well.