There are generally two types of durable powers of attorney: general and specific. General powers allow the agent to represent the principal in all matters of any scope for an unspecified length of time. This type is useful for spouses and parents who intend to give broad powers to their agent.
Specific powers, on the other hand, limit the agent's authority to only certain areas (paying bills or making health care decisions, for example). Individuals are able to appoint multiple individuals with different powers within the same power of attorney document if they prefer. Some jurisdictions offer a springing power of attorney, which takes effect only when the principal is incapacitated.
These pose some problems, however, when financial institutions insist on verification of the principal's incapacity, which doctors may not release without a privacy waiver form. In most cases, entrusting a lawyer to execute the power of attorney documentation when necessary is the safest route. Your lawyer can also help determine which type of power of attorney to use and guide you through the process.