I did 50 miles in one day after not having been on a bike for at least 10 years. I was down for a week after that. And I thought I was in decent shape from running on a treadmill a couple times a week.
What kind of bike will you be riding and what kind of trail? "Developed' as in paved? If it is I recommend NOT doing it on a mtn bike that hasn't seen the light of day for 10 years and still has the giant knobby tires on it.
Good luck.