Welcome Back Jeremy!
I hope you are having a magical week! I’ve found that for the more popular rides, the FASTPASS tickets do tend to run out somewhat early, but you’d be surprised at which rides may still be available for you. I though Toy Story Midway Mania would have sold out quickly at Disneyland Resort because the same ride at Walt Disney World does, but sure enough, we were able to still grab a
FASTPASS in the afternoon for that attraction at Disney California Adventure on our last trip.
Each day can be different as to which ones will go quickly, but in my experience, Radiator Springs Racers is the attraction to run out the fastest. Soarin’ Over California was another popular one during out last visit, as well as the Matterhorn Bobsleds. But again, it really depends on the day and the crowds. I would advise you get the FASTPASS tickets for the attractions you most want to see, and check the wait queues on the other attractions throughout the day as sometimes the lines are short on a ride you wouldn’t expect it to be!
I hope this helps and let me know if you have any other questions as you are planning your visit.
See you real soon!
-Emily