Certainly not. But they're common defaults. The worry is that if someone picks a non-standard interval, it suggests that they gave conscious thought to what int

Certainly not. But they're common defaults. The worry is that if someone picks a non-standard interval, it suggests that they gave conscious thought to what interval to pick and came up with that one. The natural question in that case is why: Is there some economic reason that 12 years would be special, or some matching limitation to their data set? Or did they try every interval between 5 and 20 years and pick the one where the result was most favorable? Edit: But it sounds like it actually was due to the size of the dataset: https://news.ycombinator.com/item?id=9222416 https://news.ycombinator.com/item?id=9222416