Depending on how you've stored them, they'l easily last a few decades
BUT
Its always best to try to keep your stock somewhat fresh. What I usually do is cycle my batches. Continue to make batches as needed, but when shooting, use the oldest rounds. They'l rarely get to a point in age where you should be concerned, it keeps you busy, and gives you a chance to make room for your new special loads.
I have so many different types of .223 rounds laying around here its ridiculous, I feel like an honorary Somali (-06, .270 & 12gauge to follow)