There is an increasing interest in using temperature to ensure safety in MRI. We designed parallel transmission RF pulses using either SAR or temperature constraints and compared to each other and unconstrained RF pulse design in terms of excitation fidelity and safety for four different RF exposure durations (from 6 mins to 24 mins). We found that the benefit of using temperature correlation matrices on RF pulse design diminishes as RF exposure duration increases. However, safety of the subject is always guaranteed (the maximum temperature was equal to 39°C). This trend was observed in both head and hip regions, where the perfusion rates are very different.