According to the opening of the Shulchan Aruch’s section on Pesach, one should start inquiring into its laws 30 days in advance of the festival.
Early commentators offer different rationales for why we need to swot up on Pesach right after Purim. Some say that there is simply a lot to know — how to bake matzah, search for chametz, kosher dishes, set up the Seder; others point to the wheat that needs grinding and other foods that need preparing in the weeks before Pesach as the reason.
The Israelites left Egypt fast. There was not enough time even for their dough to rise. These days, however, ever since the Jewish calendar was regularised, we have plenty of warning when Pesach is around the corner. We start planning (at least) a month ahead. Hopefully, we will reach the Seder, having done all we can to make the festival as beautiful and meaningful as possible.