Cajoles will need a proposed end date in order for them to be fulfilled and/or delivered.
One example of a Cajole that wouldn't work would be to ask someone to never do something again for the rest of their life. If they were to accept that, how would they ever get paid?
Instead, give a more realistic time frame when challenging someone to do something. For example: “JIMMY KIMMEL: We will pay you $10,000 if you don’t perform your monologue for 1 month”.