From the guides I read they state that from March to May you can visit the Keukenhof.
If the winter is warmer flowers will bloom earlier. What happens in such situation? will Keukanof close earlier (before may=, will it still be open and "shiny"? If open are there still blooming flowers?
Eg.: 2014 was a warm winter. I heard some people comenting that the Tulips bloomed much earlier and the Keukenhof was not so beautiful anymore. I am not sure how reliable this was, and if they knew this for a fact.
Note: I rephrased the question and made it a bit more generic.