Indeed, initially you really do not know, but then after 7 to 10 years of information coming in (Statements, sync checks, PRO royalties, pay pal transfers) You do know. So I say give your music to those who give you money every month or every quarter. I do have tracks with companies that rarely produce income. I do not send them new music and sometimes ask them to eliminate my catalog from their web site. The “cut off” occurs with companies that do not produce meaningful revenue. I do not consider $250 to $500 a year to be meaningful.