Shocks are a funny thing.
They are capable of lasting a VERY long time in certain conditions.
Down here in Florida the roads are pretty good, and the terrain in pretty flat.
I see a lot of cars in the yards that still have the original shocks. (yes I grabbed them)
I would say - if the shocks are still functioning properly - go ahead and use them.
If they have failed - then don't.
If you rock the car up and down - the shock should steady the travel in a few cycles.
They do not support any weight - they just act as a buffer to stop the bouncing.
If you are happy with how the car drives - then why change it?