This really needs to be posted in the Real Estate or Probate sections.
A usufruct is binding on a buyer IF the document creating the usufruct is filed.
The answer to the rest of your question is: it depends.
Usufructs that are created by contract or by the terms of a will or trust can pretty much stipulate anything under the sun for the terms of the usufruct. A usufruct created by operation of law -a death of a spouse with no will, for example, would terminate with remarriage and for other specific reasons. So, like I said, it depends.