My park is almost 60 years old and still going strong.
Throughout the 60 years my parks landscape has changed, rides have been removed, replaced, enhanced, new rides were built, scenic details were put in or replaced, new themed areas have been added, I have a completly underground rollercoaster that is very popular and has a 7.0 rating, plus I still have some rides that are over 57 years old and have not crashed once, etc.
How old is your oldest RCT theme park?
I wonder if anything will happen when my park turns 100. That is my goal to find out.