Banner fatigue occcurs when the consumer has seen a same banner or creative too often and gets bored and no longer notices. In the best cases banner fatigue leads to CTR decrease and in the worst to irritated consumers.
Banner fatigue can be managed by setting capping and renewing creatives.
Banner fatigue is typically an issue in retargeting campaigns where frequency is high.
Banner fatigue is also called banner burnout and is different from banner blindness.