Sara- Timing and planning makes a difference. Since the N. Rim of Grand Canyon is still closed; I'm guessing your R2R was a walk to the River and back from the South Rim- an 18 mile walk if gone down to Phantom Ranch and back- in very mild weather (the inner canyon at below 80 degrees).
The R2Rs mentioned here include the N Rim-1000' higher; and 21 miles from Rim to Rim. Steve's walk had mild weather-making it comfortable. Its still doing the last 4 miles UP 4000'; where the S Rim R2R is 3000' in 3 miles at lesser altitude, and shorter distance.

I'm not dismissing your walk; just pointing out differences so you can compare walks and degree of challenge. I often do the walk at this time because the weather and spring blooms in the canyon make it a nice day hike...