I did an ultra last year and broke the 12hr barrier. When I did it, I’d never done one before. The longest run in training was 18 miles so I’d never run a marathon before either.
Now I’ve done both by doing that ultra, trying it again but a bit quicker just doesn’t feel like it would be as much of a challenge. I guess that’s the reason I’m not driven to do another one.
As you will be well aware, the commitment to training is no small undertaking. I also found that all that endurance trailing impacted on my ability to produce short, high power bursts which means the mountain biking I do for fun is harder than it used to be.
Maybe not so he inspiration you wanted, but it might help you realise that one is enough. It’s more than most folk manage!