They usually boost the brilliant spawn towards the end of an event. (Which isn't the best time for you, but before work, say.) Don't give up, keep your eyes peeled. If you're stationary, and not prone to gps drift, regular spawn last for 30 minutes, so turning the game on every twenty minutes to check will make sure you get anything that's there. And if you're lucky enough to have gps drift working for you (tablets seem more prone to it than phones do), leave it open and running and you'll get a few more.

I had a similar problem with Brilliant Sirius, and ended up seeing more in the last few hours than I had most of the previous week.