[pascal_cuoq]

This article lists some real examples that require more than 512 bits: https://res.mdpi.com/d_attachment/mathematics/mathematics-03...

Note that digits of precision are expressed in decimal unless explicitly given as “bits”, so that the phrase “10,000-digit arithmetic” really means around 33,000 bits.

[tgflynn]

Certainly if you have errors that grow exponentially all bets are off. I wouldn't think that would apply to simply summing a set of numbers though.