We don't currently offer a shelf life as out of the box searchable criteria. Shelf life is a complex field involving a UOM on the trade and even more attributes on the material spec. This type of query can be handled today with a report with multiple parameters. You can use our custom report configuration to provide parameters in the PLM4P UI and add a link to this report on the trade spec and material spec search page. You can learn more about your reporting options in the Reporting Guide.
If you think the search can be done without specifying the other attributes, you could also do this with a search customization. For example, if your trade shelf life search is always in years and users wouldn't need to specify a unit of measure when searching then you can customize the trade search to include that criteria.
The following thread discusses how criteria can be added to any search:
Hope this helps. We are always here to provide guidance so if you have any questions let us know.