For permanent employees, I would definitely agree - anyone who is unable or unwilling to stay in a permanent position for more than a year, say, probably isn't going to be a good bet in the long-run.
For contractors, it's obviously somewhat different - but speaking from experience, many short contracts tend to get extended, so someone who has a raft of 1-2 month contracts and very few longer ones might be a bit of a risk. (Obviously some contracts are intentionally short - but I would definitely describe a very short contract on my CV as being more of a "project" than an actual contract.)
For contractors, it's obviously somewhat different - but speaking from experience, many short contracts tend to get extended, so someone who has a raft of 1-2 month contracts and very few longer ones might be a bit of a risk. (Obviously some contracts are intentionally short - but I would definitely describe a very short contract on my CV as being more of a "project" than an actual contract.)