mixing milk frozen on different days

abbyful

So far I haven't had to use any of my freezer stash. But when I do, is it okay to use milk from different days in the same bottle? I have some bags that are only 1.5-2.5 oz, so I was wondering if I could mix them when it comes time to use them. I can't think of a reason why not, but figured I'd double-check just in case.