When searching for storage conditions or recommendations from a product’s supplier, most folks search for the MSL level. Not all datasheets will list an MSL though, and in many cases MSL may not even apply.
For example, Kingbright’s WP424IDT datasheet lists “Product in the original sealed package is recommended to be assembled within 72 hours of opening”, but this is not related to the Moisture Sensitivity Level(MSL) of the part.
Per JEDEC specifications, MSL is only assigned to surface mount devices (SMD). Parts not designed for SMD mounting will not usually have a specified MSL. The manufacturer will instead provide product handling information.