We automatically exclude anyone who has a string of positions they've kept for only a year or less. If someone can't show that they stay at least two years then

We automatically exclude anyone who has a string of positions they've kept for only a year or less. If someone can't show that they stay at least two years then it's not worth it to us to bother bringing them up to speed on our code base. As you say, there can be exceptions, but it's generally a big red flag and a sign that someone is overpaid and arrogant to boot.