Service-Stations: There was never an offer of cleaning displays I could read about in German forums. They change displays for free in guarantee period, sometimes one time only, sometimes four times and sometimes out of guarantee period, but mostly they make an expensive price offer for changing the display, if you ask after the first year.
Only in the last case I would wait a bit, look if more dust collects under the display, until now it seems to be not as much as I would open the display.
The two years warranty never works: You have to proof, that the fault is manufactured and there from the first day. I think, thats it, where its at, but you see, here in this forum participants seem to rule the theory, that the fault is a development under heat conditions.