Usually ELISA microplates are not given a shelf-life on account of the fact that they are not considered perishable. But some vendors do provide an expiration date. The ELISA microplates generally have a shelf-life of 3-5 years after month of production.
ELISA microplates are generally very stable laboratory consumables. So, in order to maximize the shelf-life of microplates, they should not be exposed to extreme conditions, such as extreme heat or cold. Always refer to the vendor documents for recommended storage conditions so that its shelf-life can be extended.