Of course, there are strict rules regarding the replacement: the charms and amulets are never thrown away, they are brought to a shrine (preferably the same from where they were bought), to be burned in a ritual fire called Dondo-Yaki.
But like most of the Japanese religious events, the burning of the charms is also an opportunity to have fun and good time. The fire is an attraction by itself and some of the burned items are adding to the spectacle: the large Daruma Dolls are randomly exploding with loud "bangs", sometimes being projected out of the fire...
EXIF info:
Nikon D300
Lens: 18-70mm F/3.5-4.5G
Focal Length: 34mm
Aperture: F/7.1
Shutter Speed: 1/320s
ISO Sensitivity: ISO 400