I think spring (April and May) and then a little around October up here in the midwest. Spring time they are dragging out the old gunked up grill and looking at it and saying, "damn, I really don't want to clean out this mess and get rid of the mouse nest. I should just buy a new one." So they push it off to the curb and head for Home Depot. In the later fall, people up here are ending their grilling for the summer and realize there is no room in the garage and they don't want to leave it on the porch all winter and have to shovel around it, so they shove it off to the curb with plans to hit Home Depot in April.