Adjustable-depth assemblies for luminaires and other devices

A method of securing a lighting assembly relative to a support structure, the method comprising:

• affixing a centerplate to the support structure, the centerplate including a plate opening and supporting a lighting electrical box that includes an extendable sleeve and an electrical box housing, the extendable sleeve being slidably received within the electrical box housing, and a front opening of the electrical box housing being spaced outward from the centerplate by a first distance;
• and
• after a support structure covering has been installed on the support structure and around the electrical box, adjusting the electrical box relative to the centerplate and an outer surface of the support structure covering by moving the extendable sleeve within the plate opening between a retracted position, in which a front opening of the extendable sleeve is spaced outward from the plate opening of the centerplate by the first distance, and an extended position, in which the front opening of the extendable sleeve is spaced outward from the plate opening of the centerplate by a second distance larger than the first distance.