If you're currently in school or university holidays without a regular schedule of academic pressures, you can still use the program techniques. In fact, it may even be easier to develop because you have more available time to invest.
What's important is that you develop the skills. As long as you have material to practise the skills, there is no problem!
Recommendations and tips
Find some material that is somewhat relevant to you or that you are interested in. It could be material for your upcoming year.
Look at study designs or learning objectives (this is almost always publicly available for your course curriculum as a PDF document). You can study things that are related to the learning objectives.
Don't worry about covering the upcoming year's material perfectly. Even if you study some things that aren't relevant, remember that the primary purpose is to develop the skills. If you have the skills, the material is no problem, and whatever you do end up pre-studying is just a bonus.
Remember, if you pre-study the whole year's material in advance, without developing the skills properly, you lose. If you develop the skills without studying anything relevant to next year, that's still a win.