If you know the decorations are not going to be eaten, you can make them as long in advance as you like. Figures last for years without being damaged.
But if the answer is yes, don’t make them too far in advance, since the longer that passes, the harder they will be. Still, you can make them several days in advance and keep them.
Take note, because I leave you several tips to preserve them, whether they are to be eaten or not.