Storage bags

Ftm and I know I have a lot of probably really dumb questions but there id's no manual too any of this.

So here's the question, when pumping I'm only getting around 30 to 40ml per pump sitting of 10 too 15 minutes and so sometimes it takes 12 too 24 hours too have a large enough supply too put in a storage bag.

Is it safe to mix 2 or 3 diffrent days worth of milk into a bag together?

Do I have too freeze the bags or can I leave them in the fridge since my little one goes threw milk quick?