An intact automatic watch should withstand normal sporting activities and shocks like fast cycling over cobblestones; if parts come loose, this points to a pre-existing damage or improper prior use, which when buying second-hand watches via eBay without warranty is a known risk. For extreme stresses sport or diving watches with screw-down crown, thicker glass and stable case are better suited. Signs of a due service are deviations of more than five seconds per day or a clearly reduced power reserve. As an interval, about four to five years is recommended on everyday watches; on rarely worn watches only when problems appear, except on rare movements with difficult spare-parts supply. Letting watches sit without movement harms them; a service usually costs several hundred euros.