I think if you decide to not cut Felix's nails, it is still important to inspect them.
The 'dew claw' is high up the front paws, and if that nail grows around, it can puncture the pad or skin. If nothing is happening to the surrounding tissues, I guess it doesn't matter how sharp the nails become. Personally, I don't like getting shredded when they jump on my back. So, I walk around like a 'gunslinger', clippers in my pocket, ready to clip anyone's nail that looks too long.

Welcome to PT.