I'll agree with most everyone here, having been where you are not very long ago. My wife and I started with short rides, and they made us sore. When the short ride didn't make us sore any more, we added some more to make us sore, then the next day rode the short ride. So we alternated. Pretty soon we were up to about 12-15 miles...then 30, then more, without making us sore. Now, and I'm talking literally less than 3 months ago, 50 miles doesn't make us sore, or at least not enough to still be sore the next day.
"It hurts so good..."