Is It true that seals on water pumps usually start leaking after around 5 years? why how depends?

I have heard that even Toyota OEM water pumps start to leak around 5 years, but if true, why is this? is this the one of the MAIN reasons to get your water pump, coolant and timing belt replaced every 5 years or 75, 000 miles? the water pump is just as important as a timing belt? and just as difficult to replace? show more I have heard that even Toyota OEM water pumps start to leak around 5 years, but if true, why is this?

is this the one of the MAIN reasons to get your water pump, coolant and timing belt replaced every 5 years or 75, 000 miles?

the water pump is just as important as a timing belt? and just as difficult to replace?
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