Accelerated laboratory experiments have been conducted to study the change in latent heat of fusion, melting temperature and specific heat of commercial-grade stearic acid, acetamide and paraffin wax subjected to repeated 300 melt/freeze cycles. The latent heat of fusion, melting temperature and specific heat of the samples were measured after 0, 20, 50, 70, 100, 150, 200, 250 and 300 thermal cycles using a differential scanning calorimeter. Acetamide and paraffin wax were found to be more stable phase change materials (PCMs). However, acetamide absorbs moisture from the surrounding atmosphere.