The top-up four to six weeks later is the appointment that slips most often, and it's the one that decides how the work finally looks. Scheduled at the first session, it stops falling through.
On long appointments a deposit isn't strictness, it's protection. Three hours that nobody turns up for is a lost day; a deposit taken at booking all but ends it, and announced in advance it is almost never questioned.
Around that sit the parts that quietly do the reassuring: aftercare messages timed to the healing week, and a record that keeps consent, the patch test, the pigment batch and the before-and-after photographs in one place — evidence if it's ever needed, and the working basis for the top-up either way.