It is recommended to spend at least two to three days in Hawai'i Volcanoes National Park to fully experience its diverse landscapes, volcanic features, and hiking trails. This will allow you to explore the main attractions, such as the Kīlauea Visitor Center, Crater Rim Drive, Chain of Craters Road, and various hiking trails like Kīlauea Iki Trail and Thurston Lava Tube. However, if you have more time and want to immerse yourself in the park's beauty and unique geological features, you can easily spend a week or more exploring the park.