Q: Has collective Sadhana any advantage over individual Sadhana?
Yes, it has.
Q: Has it not disadvantages also?
It has some. It is an advantage to those who are less advanced and a disadvantage to those who are more advanced. Collective Sadhana always requires somebody who can create the necessary atmosphere — not by anything else but his presence.
Q: How could the disadvantages be overcome and the burden on the leader or leaders lightened?
As I have just said, it requires somebody who can keep off certain forces and at the same time create an atmosphere by his presence. For instance I meditate with you here but I do not come out with the same consciousness that I have when I am insider. The burden is not a question of any individual. No one can help it.
– Sri Aurobindo