Depends on whether you're tracing through the male or female line.
In the pre-modern period, most men live and die close to where they were born. Many women do too, but many others migrate to other areas as a result of marriage - they marry an itinerant worker, for instance, and settle in his community, which may be a little distance away.
So, if you're tracing through the male line, you'll often find the family stable in one district for several generations.
Still, there are periodic upsets, whether throug war, dispossession, famine, etc, that see significant numbers of people moving of necessity. These come along ever few generations. So stability over many generations in the same location is the exception rather than the rule.
That's not to say that the people living in a particular townland in, say, 1800 wouldn't be descendants of people who lived in or near that townland in, say, 1500. They might very well be. But they would be a minority; most of the descendants of the people who lived in that townland in 1500 will be living in other places in 1800.