When I re-evaluate my current *G FFP (A3), I do the following:

1. Identify one or more other FFPs with low mileage thresholds for qualification / maintenance (eg TK, OZ).
2. Identify the several *A carriers I am most likely to fly with in the near future.
3. Check the miles crediting rates for carriers in 2 with current FFP / FFPs identified in 1, for the classes I am most likely to fly in.
4. Identify which FFP credits the most miles for my likely flying patterns, sufficient to reach their miles threshold.
5. Realize that I may not be able to choose the cheapest fares if I want to achieve the miles required for 1, when flying with 2. Cost some possible itineraries with carriers in 2 in order to see how much more I may be paying to get *G with 1.
6. Stay with current FFP, or change to new one.

Easy.