[sAbakumoff]

I heard of 8 years. In 5 years you can optionally apply for Dutch citizenship and if it's approved 30% rule is gone.

[mtrimpe]

It used to be 10 years but was reduced to 8 a few years ago.

You keep the 30% rule after you apply for citizenship though. It even applies to native residents who haven't lived in NL for more than 10 or 20 years.