I noticed a couple of you have short 5 and 16 miles is the farthest, ask any of those 24 hour riders how many miles they did when they first got started in cycling, these things take time. I have a limit, I can't ever, even in my prime when I use to race, see myself, nor wanted to sit in a saddle for 24 hours cranking out huge miles, it's just not who I am. But I started out short too once at probably 1 mile, so don't feel embarrassed by doing some short small mileage thing, we've all been there, and eventually you move upward in the mileage department and settle on a max distance that is comfortable for you.