OK, so I know this is a highly subjective question, but after an endurance event how long should it take to recover back to normal strength/fitness?

I did my first 12hr solo at Bontrager 24/12 9 days ago now, and finished quite strongly in 14th out of 37 riders (better than I was expecting at least). Obviously, I put 100% effort into it, and was expecting to be pretty tired for days after… As it happened, I actually felt OK with no significant aches or pains for normal day to day activities pretty much straight away.

But then yesterday I got on the bike for the first time in a week. I was as weak as a kitten, and struggled to turn my legs over on any kind of gradient! I’m not the most powerful of riders anyway, but I was straight into the granny ring at the sight of a climb 🙁

Is it normal? How soon should I be back to normal? What should I do to help myself recover? Been thinking maybe just a few gentle road miles might help, is that wise?