When run continuously, cf-execd will execute its exec_command every CFPULSETIME seconds after it has encountered any AddTimeClass-based hard class which has ever been set. With the default schedule, exec_command, and CFPULSETIME definition, for a cf-execd that starts at 00:00:00, it will run every single minute until it is terminated, or CheckNewPromises returns RELOAD_FULL. This is easily observed with -Fv as the following excerpt indicates:
cf3> Reference time set to Fri Nov 30 14:19:52 2012
cf3> Checking schedule Min00...
cf3> Waking up the agent at Fri Nov 30 14:19:52 2012 ~ Min00
The hard classes are not being reset as they should, so that, for example, any uninterrupted hour long run of cf-execd without a new promise will accumulate enough MinXX classes to make it think it is ALWAYS time to run. The hard classes should either be completely regenerated on each run (as with RELOAD_FULL) or the time classes should be selectively removed each time they are generated (what I've done locally).