I think my kids were breast fed for 2-3 months and then another 1-2 months from frozen milk and finally a gradual move to formula by mixing the breast milk and

I think my kids were breast fed for 2-3 months and then another 1-2 months from frozen milk and finally a gradual move to formula by mixing the breast milk and formula so that there's no sudden transition if the child isn't used to the taste, etc. No qualms at all about using formula within the first 4-6 months.