No election conduct in trust. Trustees are appointed as per trust deed or by board with 2/3rd majority.

1 year.

It would be once in 3 years or so asper public trust act of your state 

It's a per the bye laws of the said trust and normally three years

Trust is a form of organization which is formed by obligation annexed to the ownership of the property, and arising out of confidence reposed by owner. The author or will maker transfers the property to be used for a purpose. If the objective is to benefit few individuals, it becomes a private trust and if it uses ‘property’ for common public or for community at large, it is called a public trust.

Elections take place once in 5 years to elect 545 members for the Lok Sabha (Lower house).

Election shall be as per rules. 

Election period of trust is fixed at time of execution of trust deed. 

A trust deed has to be made and registered and the byelaws have to be stated in the trust deed.