Posting is made possible for temporary tasks to be executed in another Member State, as such the posting is by nature temporary.
After 12 months (or 18 months with a reasoned notification) your position as far as employment and working conditions is concerned is equated to Dutch employees (see applicable work conditions).
“Funded by the European Union. Views and opinions expressed are however those of the author(s) only, and do not necessarily reflect those of the European Union or European Commission. Neither the European Union nor the granting authority can be held responsible for them.”