I made a saison earlier this summer. After primary fermentation was complete I took 3 gallons of it and added Wyeast Roeselare Blend. Two months later I added cherries and pecan chips. It formed a thick crusty pellicle and has been going for about 6 months. The pellicle still has not dropped. How long will a pellicle typically take to drop?
What is your vessel? The bugs in Roeselare need more oxygen than yeast does.
I've heard that using a plastic bucket, which lets in quite a bit of oxygen, can drop the pellicle in as little as 6 months.
I've also seen people use the wooden-stick-in-a-carboy method that have dropped between 1 and 2 years.
Like @Fishtoaster said, some people wait until the pellicle drops, others rack from underneath it. If you want a decent overview, the Jamil Show had a good episode on Flanders Red that I recommend.
I've been looking around and I can't find an account of someone who had their pellicle ever drop, including one guy going on 2 years. The accepted practice seems to be to rack it from underneath the pellicle when it's ready.