I disagree , in order for a custody change there would need to be a "significant change in circumstances " since custody was decided . Some of the most common changes are :

Whether a party has provided for the child's particular health needs, handicaps, hygiene habits, and dietary and clothing needs.

Whether a party has properly overseen the child's educational and social development.

A party's ability or inability to spend time with, care for, and supervise a child.

A party's income, financial situation, employment history and capacity, present job status, and type of employment.

Frequent changes of residence by the custodial parent.