Does the differentiation capacity of Human Mesenchymal Stem Cells change over time? When should I best induce differentiation?

We have tested the differentiation capacity of our hMSC into adipocytes chondrocytes and osteoblasts over time and still see good differentiation rates after 10 population doublings i.e. at passage 5. However the differentiation potential declines with ongoing population doublings. To obtain optimal differentiation rates experiments should be performed as early in culture as possible.