Spark Plug Change Intervals

My sister-in-law now has both a 2005 and 2006 that I recently become the chief care giver for.
The 2006 is approaching 110,000 miles and I recall from someplace, that that was the mileage the book said to change the plugs. However, I can not now find that maintenance recommendation in the manual but I have found on Prius Chat 100,000 and 120,000 for other year Gen 2 Prius.

Questions: What was the original recommended plug replacement mileage for the 2006 Prius?
And did earlier or later Gen 2 models have different mileage, plug and gap recommendations?
Also, If the recommendations changed and the engines did not then would it be better to use later year Gen 2 recommendations.

Thanks
Fred14

 

Thanks