At the 200K timing belt change interval, in most cases. It also depends on the type of antifreeze used and frequency of flushes. The pump is metal, unlike the plastic pumps in BMWs which last for 40-50K miles.

The dealers and parts suppliers encourage owners to replace the pump at every timing belt change. More money for them. They now also include cam seals, which is labor intensive and in most cases not necessary.
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Keeping it running is better than buying new