It should be ok to keep them for several days. A sure sign that the time is
near is the death of the workers in the cage when you start to see the death
of many workers you can replace them from another hive. First,  remove the
dead workers then go to hive and remove bees from the top of a hive above the
excluder. doing this should buy you some more time. the longer you keep a
queen caged the more time it will take her to lay. I also is not good to hold
them more than about ten days.
 
Dean Breaux