According to the declaration of independence, when should the people have the right to change their government?

We can change the government when they are not protecting our natural rights! We know this because this declaration was made all because of the abuse of power by the king of Great Britain. The king was in a lot of debt due to war, so, he increased the taxes for the 13 colonies, there were many other thing leading to the revolution of the 13 colonies, but after, the American people didn't want to go through with it again! They knew how terrible it was, and wanted to avoid such disaster at ANY COST! So, they created the Declaration of Independence! Here's a quote from the Declaration of Independence to help "We hold these truths to be self-evident, that all men are created equal, that they are endowed by their Creator with certain unalienable rights, that among these are life, liberty and the pursuit of happiness. That to secure these rights, governments are instituted among men, deriving their just powers from the consent of the governed. That whenever any form of government becomes destructive to these ends, it is the right of the people to alter or to abolish it, and to institute new government, laying its foundation on such principles and organizing its powers in such form, as to them shall seem most likely to effect their safety and happiness."

Spanish conquistadors demanded labour from natives.