Roy Lewallen wrote:
"So the rate at which a transmission line transfers energy depends on
its length?"

No, it depends on the power fed into the line.

Storage in the line depends on its length, plus the incident and
reflected energies per unit length of the line. Velocity is fixed by
construction of the line so a slow velocity factor allows more energy
storage as the source energy output is constant and independent of the
line`s velocity factor.

Best regards, Richard Harrison, KB5WZI