I'm a south Florida resident so my timing is geared to hurricane season. I used to write the year on gallon jugs and try to rotate from there. I finally simplified my life by buying about 40 OR 50 gallons (for a family of 4)in May just before the season. Then we just drink the stuff after the season and restock again in May. Not the most economical approach but it makes one more aspect of hurricane season simpler.
Also, having kids who are notorious for taking two sips out of a large jug of water and then disavowing any knowledge of ownership, I switched to only half liter bottles (store brand of course to save bucks). When someone gets a bottle they put their initial on it and they don't get a new bottle until I get an empty with their initial. It may sound a bit draconian, but you'd be surprised how much longer the water lasts - and they get into the habit pretty quickly any how.