There are many incorrect ideas about what is true crazing and how it is caused. Many "experts" will give incorrect information and of course it is rampant on eBay.
True crazing occurs at the time of manufacture and is a result of the glaze and the clay body cooling and shrinking at different rates, therefore the glaze cracks and produces an all-over, even crazing (very fine, spider-webby lines - older pieces with "dirt" accumulation will show the lines more prominently). The effect was sometimes intentional as a decorative glaze effect and other times accidental/production flaws - sometimes both, just look at Rookwood. Some people like them aesthetically, others don't.
Crazing does not occur as a simple consequence of age. Humidity and normal use will not produce crazing, neither will vibrations. The same conditions at which crazing occurs during manufacture would have to also occur at some later point in the vessel's lifetime and would have to be extreme and rapidly occuring temperature changes. The appearance frequently called "age-crazing" is actually damage. Cracks or breaks due to trauma will be larger and more significant than the fine lines of crazing, and will also not be as evenly distributed over the vessel's surface. Even in the rare instance in which a vessel is later subjected to the conditions that create crazing, such as sitting in a sunny window or near a heat source, the piece would likely only show the crazing on the side exposed to the temperature extremes. And of course, any pottery vessel can crack or suffer damage as a result of liquid freezing in them. Using water in a vessel with any cracks (hairline or otherwise), breaks, chips, chiggers, flea bites, etc. could cause further damage - the glaze which forms the barrier between the water and the clay has been breached and the underlying clay exposed - but this damage will not be crazing.
Experience and practice will teach you to recognize and become more familiar with these things but there are also definite facts and standards that, once you learn them, will enrich the enjoyment of pottery collecting and protect you from the disappointments of myths and misinformation.