There is no need to change before the recommended 5000 mi/8000 km, according to those who have had analysis done. If you extend the interval, it could void parts of your warranty. I changed Pearl's oil a few months ago at 8000 km, putting in Mobil 1 5W30. Will do so again after a further 8000 km. Oil and filter each time. Takes about 10 min.
Pearl is a
2007 Driftwood Pearl Prius
Package "B" (everything but leather, nav, and rear camera)
Fall - to get rid of the accumulated summer pollen, dirt and grit and put in a winter grade oil.
Spring - to get rid of the accumulated condensation and put in a summer grade oil.
Since I'm running about 19,000 miles per year, that comes in about 9,500 miles per change. My last change, I tested the oil after just 7,500 miles and it had very little loss in viscosity and the other numbers were pretty good too.