First of all - defining the difficulty of any ride or event using only the mileage is foolish.

As you already know, you need to pick and choose a route, and hopefully pick a day with fortuitous weather as well.

Next comes understanding your strengths and limitations and where and when you your fitness and holding the length and number of your rest periods to that of bare necessity.

But what is missing here - is understanding that not much of your next adventure is guaranteed by the little success you have had.

Go ahead and try for your new 200 mile record, but a better means of continuing your quest toward a life involving real fitness would consider the incremental nature of exercise training adaptations.

I wonder how silly it would seem if someone came to you - told you they just ran 10 miles - so they must go ahead and try a 26 mile marathon run next week!

Carry on.