When I started as a beginner on the piano I just timed the notes by feeling. That is, until my teacher played back a recording of me to show me just how messed up my timings were. Since then I've always been very diligent about figuring out the formal beat counting pattern and reciting it mentally as I play. That went well for a while of course, but gradually the music got more complex, with irregular beats, ties, syncopation, different timings for left and right etc. A lot of the music I look at now have timings that are so complex I have a hard time reciting them, even mentally. Is there even a way to count thirty-seconds?
What do the pros do? Should I continue mentally singing the timings even if it seems to make things more difficult? Is counting the beats an absolutely necessary step in learning a new piece? Or is it just for beginners to use until they've internalized the timings?
Or do you use some kind of mixed approach where you count the slow beats and leave the faster and off-beat ones to "feel"?