There is no formula to when it is suitable to start using disposable diapers since the conditions and way of life of each family are different.
Study Note 3: What happens to the used diapers if they are not
What I wish they'd told me before I started using cloth diapers
Embracing Eco-Friendly Choices: The Sustainable Benefits of Cloth Diapers, by KaWaii Baby Diapers
Reusable diapers: Everything you need to know
EWG's Healthy Living: Guide to Safer Diapers
How Many Diapers Babies Need: Newborn Though the First Year
Diaper Need – Moms Helping Moms
Diaper Drive - Catholic Charities of Denver
Best Diapers 2024 Tested By Parents - Forbes Vetted