I think it depends on the diet and if there’s enough variety in foods being eaten. When that’s the case, you can decrease then drop formula all together and transfer to cows milk

I really wanted to but my little guy seemed to be allergic in mild cases to them all

There is formula on the supermarket shelves suitable for toddlers, so you can use it for a few years

I wouldn’t have an issue continuing formula til 3 or 4. Pretty sure you can buy formula for this age group. I would assume it’s packed with goodness