I am also an X green card. I had a green card for 15 years (1955-1970), I don't remember ever having to "renew" it, even when I spent extended periods of time outside of the US.
I also know a Dutch fellow (same guy?) engineer, very inteligent and well educated. He is not here on a real "green card". He is here on a work permit, and yes, the work permits are only good for 3 years, and it has to be for a guaranteed a job that only that person can fill because of some unique training or experience.
This Dutch guy I know is also trying to get a perminent green card. IMHO, today's immigration laws are not for the good of the country, they are for the good of the politically connected.