SERIAL columns are stored as INTEGERs, giving them a maximum value of 231-1. So after ~2 billion inserts, your new id values will no longer fit.
If you expect this many inserts over the life of your table, create it with a BIGSERIAL (internally a BIGINT, with a maximum of 263-1).
If you discover later on that a SERIAL isn’t big enough, you can increase the size of an existing field with:
ALTER TABLE raw ALTER COLUMN id TYPE BIGINT;
Note that it’s BIGINT here, rather than BIGSERIAL (as serials aren’t real types). And keep in mind that, if you actually have 2 billion records in your table, this might take a little while…