Playlists removing songs after approving

So I have had a bunch of my songs get approved within the last month of so. Nearly all of them have removed the approved songs from their playlists again. Is this accepted behaviour? What is the point of paying money to get added to playlists then? One curator literally emailed me after approval and warned me the song would only stay on for 7 days lol. This seems like a huge waste of money and is hugely misleading.