The Stamina is responsible for your character breath and can directly influence on your EXP/LOOT that you receive. It decreases in real time while you are in battle, but the hours will not back while you are online, your character needs being offline. For each 2 hours offline, will be recovered 1 hour of stamina.
Between 54:00 and 56:00 there is a small EXP Bonus for VIP Account players.
Between 53:59 and 15:00, you will have a default EXP.
Between 14:59 and 05:00, you will have a reduced EXP by 50% and LOOT by 25%.
Between 04:59 and 1:40, you will have a reduced EXP by 85% and LOOT by 50%.
Arriving at 1:40, you will not receive EXP and you will have a reduced LOOT by 75%.
Remember, Stamina can influence only on EXP/LOOT that you receive.
It doesn't influence catch.