Mixing formula and breastmilk

My baby (9months) is getting bottles that are part breastmilk part formula.

As of right now, I am making a batch of formula in the evening for the next day, as well as thawing a bag of breastmilk. During the day I pour 2oz of breastmilk and 4oz of formula into a bottle each time I need to give him one.

Would it be okay for me to pre-mix the formula and milk in a big pitcher once they are both at the same temperature? And keep in fridge until use so I just have to pour from one jug?

Not a big deal but would just make things a little quicker/easier

Thanks