According to the DB schemea, the meta_value column is of type longtext, and that has a maximum size of 4GB, however you’re unlikely to reach that.
Eitherway storing large quantities of data in a single field is bad both from a practical point of view, a performance point of view, and data storage.
I advise instead you use a custom taxonomy for this kind of data ( yes taxonomies aren’t just for post objects )