When you buy DEKA batteries on-line from Lowes, they have them shipped to order directly from DEKA. That means the battery you get was made within the last month. I ordered 1 ETX-18L for the racecar, and 1 11U1L for my lawn tractor. They took ~2 weeks to arrive, and both were made this month (March). If you pick them up at Lowes, shipping is free. Lowes' prices are competitive with other sources on the net.
FYI, DEKA is a subsidiary of East Penn Manufacturing Co., i.e., made in the USA - link to their site: https://www.eastpennmanufacturing.com/