All Heartbeat futures should have the same timeout

CHANGELOG.rst

@@ -5,6 +5,7 @@ Bug Fixes
 ---------
 * is_idempotent flag is not propagated from PreparedStatement to BoundStatement (PYTHON-736)
 * Fix asyncore hang on exit (PYTHON-767)
+* Driver takes several minutes to remove a bad host from session (PYTHON-762)
 
 Other
 -----

cassandra/connection.py

@@ -990,11 +990,14 @@ class ConnectionHeartbeat(Thread):
                             owner.return_connection(connection)
                     self._raise_if_stopped()
 
+                # Wait max `self._interval` seconds for all HeartbeatFutures to complete
+                timeout = self._interval
+                start_time = time.time()
                 for f in futures:
                     self._raise_if_stopped()
                     connection = f.connection
                     try:
-                        f.wait(self._interval)
+                        f.wait(timeout)
                         # TODO: move this, along with connection locks in pool, down into Connection
                         with connection.lock:
                             connection.in_flight -= 1
@@ -1004,6 +1007,8 @@ class ConnectionHeartbeat(Thread):
                                     id(connection), connection.host)
                         failed_connections.append((f.connection, f.owner, e))
 
+                    timeout = self._interval - (time.time() - start_time)
+
                 for connection, owner, exc in failed_connections:
                     self._raise_if_stopped()
                     connection.defunct(exc)