Do you really throw milk from bottles after one hour ?

As per the instructions, any milk prepared should be thrown an hour after but I have to say that sometimes, I misread my baby’s signs and think it’s hunger but then she only takes a few sips or plainly refuse the bottle so I leave it to be and sometimes it’s more than 1 hour.

What are the risks? Is there any (not speaking of like 6 hours or overnight) ?

Edit to add : thank you all for your feedback! I was talking about formula and have a bottle snacker baby so it’s been TOUGH to say the least 🫠