A system is AG EF terminating, if and only if from every reachable state, a
terminal state is reachable. This publication argues that it is beneficial for
both catching non-progress errors and stubborn set state space reduction to try
to make verification models AG EF terminating. An incorrect mutual exclusion
algorithm is used as an example. The error does not manifest itself, unless the
first action of the customers is modelled differently from other actions. An
appropriate method is to add an alternative first action that models the
customer stopping for good. This method typically makes the model AG EF
terminating. If the model is AG EF terminating, then the basic strong stubborn
set method preserves safety and some progress properties without any additional
condition for solving the ignoring problem. Furthermore, whether the model is
AG EF terminating can be checked efficiently from the reduced state space
