Assume you will not be back
Contractors get replaced, technicians move on, sites change hands. An installation that only its builder can maintain is a liability disguised as a job well done. Working on the assumption that someone else will open it next changes small decisions throughout: labels at both ends, spare capacity in the containment, a schematic left on site rather than in a project folder.
As-built means corrected
Handing over the design drawings at completion is common and close to worthless. Installations always differ from the design: a route changed, a unit swapped, a socket moved. If those changes are not carried back into the drawing, the first person to trust the document is misled. Correcting it takes an afternoon and determines whether anyone believes the pack in two years.