1990- 1999 is the complete set of teaching materials worth collecting?

It's worthless You can collect it yourself if you like. But there is no possibility of any value,

First, because the age is relatively recent and there are many, the collection pays attention to the scarcity of things.

Second, because there are many publishing houses, the information is relatively developed, and there are almost no treasures.

Third, collection should pay attention to efficiency. Without efficiency, you may lose interest. You can find some textbooks that are a little farther away, such as those in the Republic of China and after the founding of the People's Republic of China, which have certain value because of the influence of the social environment at that time.