This is a great approach!
I assume you’re using a PAO approach since you mentioned flipping sets of 3 cards at a time. Remember when you are practicing for recognition to isolate the P’s, the A’s, and the O’s per card individually. More on this here: Tip for practicing PAO
The gradual pushing of your speed is smart too. I think if you stick with it, you’ll see results fairly soon!
Just remember it takes more effort to go faster the faster you go. Going from 3:30 to 3:00 is about a 14% time reduction for a 30 second decrease. 3:00 to 2:30 is about a 16.5% decrease to chop 30 seconds, and going from 2:30 to 2:00, again the same 30 second decrease, actually involves a 20% time reduction. This effort needed scales up rapidly the faster you try to go.
If you ever push yourself to get under one minute, think about the difference between going from 3 minutes to 2 minutes (a 33% decrease) versus 2 minutes to 1 minute (a 50% decrease.) It gets tough.
Thats not to discourage you, but to advise you to be realistic about the effort needed so you don’t get frustrated if you hit plateaus of progress as you get faster!