When should you replace the Strut Coils on a 2012 Prius C?

Hi All

My daughter has a 2012 Prius C with about 110,000 miles on it. She bought it used with one previous owner. The vehicle looks like it was relatively well maintained.

When should you replace the strut coils on it? Is there a set maintenance timeline or miles for it or is it only when you see cracks in it or do you measure the height of the ride?

Also, how often do you change the strut?

Thanks