More important that miles logged is losing weight..Now we all know that most of us are chubby darlings..
20lbs less around the middle has a training effect that overrides miles.
If anyone can lose a few lbs a week until ragbrai, they could meet their goal.
Miles are overrated.
500 is enough unless you are retired, when you have time to ride.
I do agree every pound you shave off makes a big difference in riders abilities. But saddle time is just as important. You need it to toughing up your rear to that saddle. You also need back to back long mile training days. As in above 60 miles. The hardest thing about RAGBRAI is the average 75 mile day for seven days running. Without body conditioning. By mid week, you could be miserable. A few folks are lucky and don’t need all the miles. But the vast majority of us do. Me included. If you are not comfortable doing a solo 60-100 mile ride. Join a bike club in your area. Most have endurance rides. Those long rides will be a test if your up to it. If you feel OK on day 3 after doing two 60 mile day in a row. You wont have any problems.