When to use freezer stash?

Ok so my baby is 2 months old and I’ve been exclusively pumping since birth. I’m a SAHM and usually give my baby freshly pumped milk, and will freeze all the extra milk at the end of the day. Since I am an over supplier, I’ve been able to build a good large freezer stash so far. I have about 1200 ounces of milk in my freezer which is enough to feed my baby for a little over a month.. My question is, when should I start giving my baby frozen milk?? My plan is to stop pumping when baby is 6 months and have enough freezer milk saved up to last until my baby is 12 months. I track everything in an app and it says I should be able to achieve my goal on time based on my supply. I know that breast milk changes as baby gets older, so I just don’t want to be giving my baby frozen milk from January (when they were born) when they are 6 months old, since they will have different nutritional needs by then.. So should I start giving my baby frozen milk already, and just continue to pump and freeze milk? What’s the best way to go about this??