Consult a supplier of MDEA, if possible. The supplier usually has a product handbook or equivalent that explains how a product could degrade and the rate mechanism associated with the degradation. For example, many organics dimerize with a rate constant that is a function of temperature.
Check Kohl's Handbook and "Ball" article published by Gulf. Using my poor memory, thermal degradation starts to rapidly increase at 260 Deg F for amines. I believe thermal flux to reboilers should not exceed ~30,000Btu/ft2 hr as well.
