These issues should all be consider

These issues should all be considered in the decision of an optimal hold time. A practical lower limit was selected that minimizes the adverse effects of all these competing factors. Longer hold times beyond 70 seconds were also considered for investigating the long-term creep behavior. However, experimental conditions preclude setting the hold time for creep testing to longer than approximately 70 seconds due to issues such as tip depth saturation (the maximum indenter piezo depth range for our module is 50 µm), introduction of nonlinear viscoelasticity at high strains, non-convergence of the selected creep compliance model to experimental data, incompatibility of feedback loop parameters with the loading programs, and instrument instability.