I used the Ben Harden method to raise my queens with great sucess last year. http://www.dave-cushman.net/bee/benhardenmethod.html
This year I didn't take it as seriously and my success has been poor. Yesterday, I tried again but seriously and followed the book. There was one remaining capped queen cell from my previous weeks grafts in there as I put in 26 grafts yesterday. This got me to wondering. Can you put multiple waves (ie a new set every 5 days) of queen cells in the same hive and have them raised with success?
Not knowing the answer I opted to remove the queen cell but in the future I'd like to know if I could simply leave them alone and run multiple waves of queens at the same time in the same queen rearing hive. The hive is being fed 1:1 syrup and there is a healthy young queen laying steadily below the excluder.