I know they say before 12 months. But It's really expensive. I am trying to keep costs down and e eats really well. Fruit, veg all home cooked meals I freeze in advance. Eggs, fish anything really. No concerns with his weight or milestones. Would it do any harm if I used full fat cows milk?! He just doesn't seem to like the formula anymore and it's expensive. Is it unreasonable to do it to keep costs down?!