Greetings David:
Those of us in the forestry and ecology fields tend to look at forest/tree maturity or life cycles in two general ways: biological maturity and economic/financial maturity. However, your question is more closely related to the tree vigor/health of a yard tree. This sort of judgment often requires on-site evaluation by a trained professional forester, arborist, or horticulturist.
If you are interested in utilizing these trees before they lose their usefulness as timber, then these trees may need to be utilized in the near future; however, I can't make that judgment sitting in front of my computer monitor. If you truly want to get an expert opinion, then you really need to contact a professional for an on-site assessment.
Best of luck!