If you have, for example, one Bracelet for W1 Saturday and one Bracelet for W2 Sunday, you will need to activate each Bracelet to the correct weekend in your Tomorrowland Account. 

Pearls are valid per weekend. You cannot use the Pearls you charged one weekend, during the other weekend. 

Refunds: If you have topped up each Bracelet online, you will receive an automatic refund for the remaining Pearls. If you have topped up each Bracelet at the festival site, you will need to fill in a manual refund form for each Bracelet.