D1 或 D2 签证是否包括延期？

No, if you purchase the D1 or D2 visa, you get a multiple-entry visa with a total validity of 1/2/5 years. Each visit allows you up to 60 days of entry.

If needed, you can extend each stay twice for 60 days each. So each stay can last for up to 180 days. An extension needs to be purchased separately.

For each extension, one personal visit to the immigration office is required.