THere are maps of the Big Island showing all the lava flows of the last 1000 years. Puna has had active lava on 90% of the area in the last (IIRC) 1000 years, or it might even be more recently. Many of the flows are recent. I lived there for some years and used to find hiking around the National Park Kilauea area great fun. The lava from both active Big Island volcanoes is fairly predictable but has almost reached Hilo a couple of times, I think once in the last 20 years.
Puna is a district on the southern tip of the Big Island. Are you saying 90% of Puna, or 90% of the Big Island was covered with lava flows in the last millennium?