If you left the spindle running for hours at a time ( lots of hours, but less than a day) at higher speeds, the count will overflow 32 bits. Going to 64 bits prevents it from occuring. (Overflow occurs in 64 bits in longer than a year.) Practically, not that likely, but possible. I had dreams of releasing software, and I take safety seriously. I wanted to essentially prevent overflow. So I implemented it with 64 bit math. It's not that easy to test this kind of problem, especially on an Arduino platform. If there was an ICE, maybe I would think differently.
On my processor of choice, Teensy 4.1, using 64 bits has practically zero overhead. Might have a far bigger impact on weaker and less capable processors. I'd rather be a sport and spend $32 on the processor than being hamstrung by an inadequate processor. Already lived that experience once, my development time is more valuable than the $28 I would save for a cheap processor. My ELS runs, so my choice paid off handsomely for me.
