Quote from Traveler:
The signs are...
1. You've already made your year's salary and the year is not even halfway over.
2. You start noticing all the money your real job is costing you by not being at the trading job.
I can vouch for #1 since last month (knock on wood). #2 is harder to judge.. I'm more worried about not being able to execute at crucial entry/exit points than with making more profits.
Perhaps a 6-12 month sabbatical would do, but very few employers allow that.