your faster than me and I ride a road bike

I find with cadence if my legs burn I shift up the back cog, and if my lungs burn I shift down the back cog. I try to get a good balance where both are burning the same.

I will say though that after I trained myself to spin at 95-100 that I was able to ride longer on consecutive days. I didnt go faster just taxed my heart and not my muscles, heart/lungs recover faster than leg muscles.