sth finish implicitly on next calls?

[perl]

Does resuing a $sth for another call w/o explictily calling $sth->finish
causes any problem? This is because sometime I like to take a shortcut in
codes.

from this
 { ...
  $sth=&getUser("bob");
  $x = $sth->rows();
  $sth->finish;
  return $x;
 }

to this
 { ...
  $sth=&getUser("bob);
  return $sth->rows();
 }

or even this
 { ...
  return &getUser("bob")->rows();
 }

Any danger here?
thanks,
-rkl