I'm thinking, because longer pendulums travel for a greater time period through the medium of air, air resistance will have a greater affect on the pendulum bob (and string) and so the angle the pendulum travels back at would be a lot less compared to that of a smaller length pendulum?
I have uploaded a picture to help explain my question.
In case my photograph is blurry - In the drawing a pendulum is released. Then the angle that it travels to on the opposite side is recorded, so is the distance from the centre of mass of the pendulum to the hypothetical trajectory (if pendulum were to swing in a complete vacuum) distance labelled "X". If length of pendulum were to be increased, would X remain constant? Or would the angle remain constant? Or perhaps, because of air resistance, would the angle decrease proportionally to the increasing of length of the pendulum?