Every morning at 8:00, look for members whose total number of day passes used, or hot desk day bookings, will reach a milestone within the next 3 days. The milestones are 50, 100, 250, and 500. Count only bookings that weren't canceled.
For each member who is about to reach one, email a short message to [your email address]. Include the member's full name, the milestone, the date it's expected, and 2 or 3 ideas for a small surprise or announcement, such as a welcome-back note, a coffee on the house, or a shout-out.
Send one nudge per member per milestone, and don't nudge for a milestone that was already celebrated. If no one is close to a milestone, do nothing. Never contact the member, and never offer discounts, credits, or free passes.