A crystalline microporous silicoaluminophosphate (SAPO) molecular sieve is prepared by: (a) providing a reaction mixture having a molar composition within the following ranges: P:Al from 0.75 to 1.25, Si:Al2 from 0.01 to 0.32, H2O:Al2 from 25 to 50, and R:Al2 from 1 to 3, where R designates a structure directing agent (template), and wherein the molar ratios for the aluminum, phosphorus, and silicon sources are calculated based on the oxide forms; (b) heating the mixture to a crystallization temperature of between 150° C. to 250° C. to form the crystalline molecular sieve within the reaction mixture; and (c) following crystallization in step (b), aging the crystalline molecular sieve in an alkaline liquid at a temperature below the crystallization temperature from 0.5 hour for up to 120 hours. Aging can affect both catalyst life and catalyst activity.