Avoid churning the schedule by deferring rescheduling until the cumulative slippage is large.
It's difficult to know how long a project should take, and even more difficult to recover when one guesses wrong. Keep a track of how far from the scheduled times the critical path tasks are being completed. When this amount becomes too large for comfort (o.p. suggested ‘ludicrously large’), then re-work the schedule. Before that point, you keep track of a ‘delusion index’ that tells how far off the schedule you are.
The comfort point should balance the need for accurate schedules against the need to avoid excessive visits to re-work the schedule. This pattern can be applied both to tight and lax schedules.