There are 2 schools of thought.
Matt Brynildson says to add before the end, with one or 2 Plato to go. The yeast will transform some compounds, and you end up with higher levels of linalool and geranoil. So if you want floral notes, this is one way.
Vinnie Cilurzo says to crash and remove the yeast. This will keep the yeast from removing the essential oils that many are after.
So two pros use different techniques to achieve different results. I think one needs to decide what they want in the finished beer.