The remarkable discovery of a two-dimensional electron gas confined at the interface of the two oxide band-insulators SrTiO3 (STO) and LaAlO3 (LAO) has spurred a great interest in the heterostructure leading to the discovery of a plethora of other exciting properties. Recently, the formation of the interfacial electron gas has also been shown possible when LAO is deposited on STO at room temperature, which leads to the growth of amorphous LAO (a-LAO). Here, we study the development of the interfacial conductivity of LAO/STO heterostructures with crystalline and amorphous LAO top layers in different controlled environments over time. The interfacial conductivity is found to degrade with a strong dependence on the thickness, the crystallinity of the deposited layer and the storage environment. A mechanism for the degradation is proposed and is further utilized to significantly reduce the rate of degradation. (c) 2012 Elsevier B.V. All rights reserved.