No, no. It's better than that because you normalized to a 20 mi commute and allowed the battery pack to get larger.
The fallacy that most people make is that keep the battery the same and simply use less of it, which means that you need to recharge more frequently. By letting the pack get larger, each charge cycle is an equal amount of energy so you can directly compare cycles.

So using the numbers from the paper and your values:

48v X 10Ah 80% usage = ~2000 cycles (75% was 2100 cycles, just guessing here)
48v X 15Ah 60% usage = 4500 cycles (2.5x lifespan)
48v X 20Ah 40% usage = ~8500 cycles (4.2x lifespan)

So even the mid-size pack should have roughly 2x the life-span and the largest pack is 4x the lifespan.