Online brand liquid chlorine, 10%, is on sale until Memorial Day at Atwood's for $1.99 for 128 oz. Each box contains 4 bottles, but you can buy each bottle separately. Online brand has several manufacturing plants, and one is here in Oklahoma. Atwood's keeps it inside the store, but who knows if it is kept cool on the truck delivering it to Atwood's.
Online brand uses best buy dates. Yesterday, we bought bottles dated May 7, 2021, and today we bought bottles dated May 8, 2021.
I didn't think chlorine lasted for a year, at least not at full strength.
Edit 5/31/20:
Atwood's still has the liquid shock for $1.99 per gallon. It is the best price I have seen.