How long should stucco last?

Properly installed, the lifetime of stucco is a very long time... BUT, the key being ~when properly installed, and over what substrate the stucco is applied.

In wood frame construction, more often than not, an insulative product such as metal skinned foam board is applied over an OSB (oriented strand board), or exterior grade plywood sheathing. An expanded metal lath (which cost about 50 cents per square foot) is the industry standard; however, 1" net wire (poultry Fencing) has been used for decades with quality results, and is economically more desirable ~the efficacy being subject to debate, but either way, the metal within provides the strength of the stucco wall, as concrete has very low inherent strength, is key to the products end quality ~it is only as strong as the re-enforcement within it, and the requirement of said reinforcement being properly attached to an approved substrate material cannot be overstated.

With proper installation, and annual 'patch the cracks'(the nature of life with stucco), the lifetime of the stucco coating will easily exceed 50 years; and if applied to a solid wall (concrete block/poured concrete/tilt-wall/adobe brick) ~the lifetime will likely exceed the time the building is allowed to stand.