Here's a guide
In fridge - 4 days (but i only keep for 3 days)
in freezer (the one which you also store your food) - 3 mths
in deep freezer (the separate freezer which is not with your fridge) - 6 mths (but i only keep for 5 mths)
you have quite alot of surplus. there are 2 ways to manage it.
1) you do first in first out - meaning whatever you pump out first, you feed first then you wont waste your milk
2) you do last in first out - meaning baby is always drinking the fresher milk.
I did last in first out cos i believe baby should always take as fresh as possible and that time I also had a lot of surplus so I am not so worried that I dont have enough milk. In fact I had too much milk that I threw away 40 litres of them. quite wasted I know but I still want baby to take fresh milk.
I suppose you also have over surplus of milk. If you intend to reduce the supply, then you may want to do first in first out. so that got enough to last. but if you intend to maintain, then is really up to you