Hi Chops!
I believe the quest master title is only for the season, if I remember correctly - I saw people in chat talking about missing the slave title and the quest master title before, even though I had seen them with said tags before. Which leads me to believe that earnable tags (that are not a seasonal event, such as the [Elf] tag) have to be re-earned throughout the season.
Although, I am not sure as I, myself, have never wasted my job points nor my quest points on the titles. Sorry that I can't give you a definitive answer.