The single biggest determinant of how a paint job looks after five years is the wall preparation before the first coat went on.
Filling and Sanding
Every nail hole, dent, and crack should be filled, allowed to fully dry, sanded smooth, and wiped clean before paint is applied.
Cleaning
Walls accumulate a thin film of cooking grease, hand oils, and dust that prevents paint from bonding properly. Wash walls with a degreaser before painting, even if they look clean.