Well, watch super-stretching your thumb at age 37, you might find arthritis at 60 ends your playing enjoyment. Odd pops I had in two knuckles at age 8 are requiring daily NASD pills now at 59. I'm limited to C-E span like you, and I just cheat. Nobody is going to pay me to play classical anyway. I play "Pictures at an Exhibition" which requires octave and a fifth, and I enjoy it even wrong as I play it. JS Bach Passacaglia & Fugue in C minor apparently requires octave and a fifth, but I am putting the offending notes on the other manual. For a modern pianist that writes hard stuff without a huge stretch, listen to George Winston's "Winter' album. I transcribed his "Holly & Ivy" for fun, and it is the rhythm that is tricky, not the handspan.