Five years is almost the worst case. In five years most of the people who did it last time are either in a different post or have left, meanwhile related systems have probably changed, so if they did leave documentation and if you can find it still, that may no longer be the correct process.

When Let's Encrypt was created it could have issued 3 year certificates. But it didn't because they knew that's a bad idea, the whole point of Let's Encrypt was automation, and if the certificates expire in 3 years you will say "Eh, we'll automate later" and never do the work.

5 years is far from the worst case. 50 years is a better upper bound.

Fifty years is often so different that it counts as a novel problem each time, so there's little value in knowing how you did it last time.