Depends on how much you understand. Honestly, you'll spend more time procrastinating/doing other things than studying, so it's better to understand things now than attempt to grasp a whole topic in the holidays.
It's also a lot easier to ask for help during school semester from teachers than during the holidays. That being said there are plenty of other avenues available to you (e.g. BoS!) but nothing beats face time with a teacher when you have some random or intricate question which is difficult to explain in words on a forum.