Selling rental property after 5-7 years

[Joe Sniadowski]

Ive heard on several podcasts and read several blogs/articles of people saying they sell their rental property after 5-7 years, while purchasing many more during that time.  

Besides getting the equity paid out to you, what is the benefit or reason to selling a property if you continue to make money on it each month while you continue to invest?  Is this simply to get a nice lump sum pay out from time to time?