Thanks for the tip. I just ordered 6 bags and will wait and see if Petco.com honors the free shipping promo on $60+ orders that includes multiple bags of Eco-Complete. Note the additional terms on the free shipping promo on orders of $60+, per the Petco.com website:
EXCLUSIONS: Dog food, cat food, cat litter, dog litter and wild bird seed; select oversized items, Live Fish & Rock, Live Food, Aquatic Gravel and Accents; out-of-stock items, Donations, Gift Certificates and Gift Cards; items purchased through Bottomless Bowl & More subscriptions, items shipped through white glove delivery; shipping or applicable taxes. Additional exclusions may apply and will be noted on the Product Detail page and/or Shopping Cart.