As a freelance, what would you do if the client postponed your payment(s) for a long time?

Hi , its good qustion but for me i will be with my compnay to the end , because i start with them and things was very well , so my answer i will be with my company 

its one from the inherent risk of this type of work, so you can manage it by delegate the responsibility of any contract to be done by a lawyer or to have the contact numbers of the Top Management to be easily reached to them.

Look and find another job while give them time to make the payment. Don't depend on it.