The DEFAULT_INDEX_LIFETIME_DAYS setting allows administrators to set a
default lifetime for indexes associated with database views if none was
selected by the database designer in the Design View Attributes dialog
box. This is a space-saving feature. If this variable is set, the
index associated with the view is purged it has been inactive for the specified
number of days.
Indices are purged after 45 days of inactivity
Set this option to some value below the default of 45. By setting it to
14 you will greatly reduce the amount of work the Update task is being
asked to perform.
causes Notes database indexes to rebuild?
Domino Configuration Tuner:
This setting is included in the DCT
catalog of best practices.