As an A/C certified technician there is no harm in giving the system a service.
The gas that comes out gets recycled in a automatic modern machine.
It will be low guaranteed so you know you will have the correct amount back in.
I bet your car still has the original receiver drier which is the filter.
My recommendation would be change that and it will be good for another 16 years.
I hear you Phil, but the need to change the refrigerant is a marketing ploy for a few reasons. R-134a is a hydroflourocarbon with an atmospheric lifetime of 14 years. That means, when released into the air it takes 14 years to breakdown in the atmosphere subject to UV light and other atmospheric processes. In a hermetically sealed system such as a car its life, providing the seals stay in good condition, it is pretty much indefinite. I could show you 15 year old fixed A/C plant with the original refrigerant that is working as well as the day it was installed. Every time you access a service port on any refrigeration system, there is a risk of introducing contamination, a small amount of air, a little bit of crud in the port itself and the real enemy, moisture. Then there is the tiny amount of refrigerant that is lost at the point of connection / disconnection which over thousands of cars can add up to a lot, very bad for the planet as R-134a has a global warming potential of 1430.
As a member of the Institute of Refrigeration (Yes, really, there is one!), the whole automotive A/C service process is a hobby horse of mine (I know, I should get out more). There are “special” machines which only check for leaks by pulling a vacuum. This is wholly inadequate as it is a fraction of the operating pressure (even if the vacuum was perfect it would be 1 bar, working in the wrong direction, with the running pressure up to 20 bar) whereas it is legally mandated for fixed systems to pressure test to 1.2 x the MOP (maximum operating pressure).
In any event, the take away is as Matt says, if it ain’t broke, don’t fix it. If the system is well sealed, the refrigerant won’t react with anything, the filter won’t get saturated or blocked and all will be rosy. If it starts working badly, makes gurgling noises from the dash or stops completely
then get it fixed. Oh, and run it often, as if the seals dry out then the above will start.