Most of the difference between a paint job that lasts and one that doesn't happens before the first gallon is opened. That's why we plan a real prep day into every interior project, and why we'd rather lose a day to preparation than lose a finish to shortcuts.
Prep day means furniture moved and covered, floors papered, not just dropped with cloth, but papered and taped at the seams. It means nail holes filled and sanded, cracks caulked, glossy surfaces scuffed so the new coat has something to hold onto, and stains sealed so they don't bleed through six months later.
It also means the part nobody photographs: washing the walls. Kitchens carry a film of cooking oils; bathrooms carry residue from steam and sprays. Paint over either and you're painting on a nonstick pan.
When we tell you a project takes four days, one of them is this. It's the least glamorous day of the job and the one your walls will thank you for, quietly, for the next decade.