Continuous, throughout their lifetime.
Once the eggs are released from the parent and are fertilise, the resultant embryo attaches to a solid surface. These could be the arms of the parent crinoid.
Once affixed the embryo develops and after several days will realise a free swimming, barrel shaped planktonic larvae called a Doliolaria. After a further week, these larvae become fixed and develop a stem, mouth, and five podia (arm like structures). This stage is called the Cystidean stage.
After several weeks the crinoid then reaches the staked sessile stage Pentacrinoid stage where it forms true arms, pinnules, a complete thecae and stem. Over the next few months, the animal continues to grow by adding new plates to the stem and arms so that the individual can reach a higher position in the water column.
In most cases the following year the animal is fertile and produces either sperm or eggs.
Read about the believed breeding patterns of Seirocrinus subangularis as well as the process by which it reproduced and how it was then dispersed.