The powers and position of "Administrator" have existed in some form since Wikipedia's inception in 2001. Administrators were initially selected by Wikipedia co-founder, Jimmy Wales, but before long a request for adminship process was created. In 2007, the first large requests for comments style requests for adminship reform discussion, and since then large RfCs have happened every few years.
Several powers have been "unbundled" from the Administrator toolkit—including Rollback, Template editor, File mover, Page mover, Account creator, and Event coordinator. These specific tools allow more people to help with administrator tasks without having to endure an RfA or be fully trusted with the entire toolbelt.
A procedure for de-adminship (or desysopping) has also been widely discussed. Starting in 2011, inactive admins have been automatically desysopped after one year of inactivity. Additionally, many admins have been open to recall, in which several prominent editors (typically extended confirmed editors or other admins) ask for their resignation. Then either the admin would step down, or undergo a second RfA to decide their fate as an admin.