Help Guide › Owner
Every client's page has a Follow-Up section: a switch and an interval, theirs alone.
The clock runs from their last purchase, not from when you last spoke — a personal-use pull doesn't reset it, because it isn't a purchase. Leave the interval at 0 and they follow whatever you set app-wide under Settings → Notifications, so an existing client's behaviour doesn't change until you change it.
Turning it off for one client leaves them out of reminders without switching reminders off for everyone. They still appear on Needs a Check-In, which is a list you read rather than an alert that fires.
One reminder per client, re-armed from current data every time a sale is added, edited or deleted — so an edit can never leave a stale alert behind, and a second order can't stack a second alert.