How much exercise should a 13 week old pup need?

I currently take my 13 week old JRT on 2 walks a day for 30 mins each. She's not a morning dog and would prefer to stay in her bed for a bit longer in the mornings, once out eventually she resigns herself to the fact that we are going out. Evenings she is really up for a walk and loves to play. Should I leave the morning one for now?