How long should you let an April fool prank drag on?

Somebody falls for an April fools joke. For arguments sake let's assume it was something in a newspaper or perhaps even here on GAG (like the one I had removed for trolling)

The question is when do you break the news to them what day it is?
Straight away.
Leave it a few hours
The next day
It's more fun never to tell them
Wait, the government isn't taxing potatoes to fight racism
Select gender and age to cast your vote:
How long should you let an April fool prank drag on?
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