i checked about every hour or so and randomly. i did however check LAS at one point, they had one last mon and it was opened for a good 6 hours before someone took that slot... wondered if i should send $200 just to fly there and back from LA but decided against it lol. seems like the frequent checkers at LAS is low compared to LAX/LBC.
I started looking around 3 days ago for LAX/LBC to which i found 3 opened yesterday for the coming tuesday... it did all get taken within 1hour...
Leave it open, it will close itself after a certain period of time, i usually let that be a reminder and login to check to see if anything available.
good luck!