Expressing - how long can you keep ect ect

Le

This morning I was leaking a lot so instead of wasting it I expressed into a freezer bottle thing.

Couple of questions ...

Can I keep it in the fridge until tonight and see if I can add to it

Can I add more milk to it or will it be funny because itsbeen in fridge so will be cold then me expressing warm milk into it?

Is it best just to freeze that amount once cooled down?