I'll be glad to take a break, having done all of the last 20 of them... so bored with hotlapping, I want to get back to racing! I have several other driving games sat here unplayed, gathering dust...
You can actually do them after they have expired and earn money but your time isn't saved to the online leaderboards. Just keep clicking on the trial repeatedly and even though it says the trial has expired it lets you through if you keep tapping x.