First, expecting someone to commit to only working for a short time period is discriminatory. Only certain people could commit to such a thing, such as those with a low cost of living (no family) or those who are already independently wealthy. No regular professional with obligations is going to commit to that.
Second, if you can't tell whether or not a person is a good employee after 10 weeks then you're not a good manager.
First, expecting someone to commit to only working for a short time period is discriminatory. Only certain people could commit to such a thing, such as those with a low cost of living (no family) or those who are already independently wealthy. No regular professional with obligations is going to commit to that.
Second, if you can't tell whether or not a person is a good employee after 10 weeks then you're not a good manager.