Time given patiently is still time that should be handled carefully.

Patience is easy to mistake for indifference. When someone waits without complaint, no bill arrives, so the cost seems to be zero, and the next delay becomes a little easier to allow. But their afternoon was spent, their plans were held open, and their good grace was the only reason it felt free. What they gave you was generosity, not permission.

Treat a patient person as the one you most want to be on time for. Tell them a revised time as soon as you know it, rather than when they ask. And say thank you for the waiting itself, since almost nobody does.