Book of Orbs has been really bad last weeks. I have not been able to place any order with low fees last three weeks or something, all failed. Before that those low fee orders placed with delay of about one week or less.
Counterparty has just released an update today and has plans to reduce XCP transaction fees even further. So hopefully BoO will benefit from the latest and upcoming updates too.
Consider right now the Bitcoin blockchain has a huge backlog of transactions and fees are higher than usual.
https://counterparty.io/news/counterparty-development-update-20170518/