We have a 20-year-old OTIS hydraulic elevator (5 floors) Our maintenance company is recommending we change the Hydraulic Oil for $8750 since our elevator is over 10 years old. Our maintenance company has been maintaining the elevator since it was installed 20 years and never recommended an oil change before. There is no reason given other than age. Questions:

Do we need to change the oil?
Why didn't they recommend changing the oil 10 years ago? Is this a new requirement?
Should we wait for a malfunction?
Is $8750 a fair price? Plue $2500 to dispose of the oil - $11,250 total

We are in San Diego