My primary goal for 2019 is to complete a 300K. At the end of most 200K rides I've done thus far, I was more than ready to be done riding for the day. I have been pushing the envelope a bit as a friend has a 200K perm that starts 4 miles from my house. And it is actually a 211K route so by the time I ride from my house, do the route, and ride home, I've put in 141 miles (226K). I have done a 200K on a Saturday followed by a 100K on a Sunday a couple of times. But I still haven't found saddle nirvana yet in spite of trying several different saddles as well as cycling short combinations.
I'm thinking the 300K I will do will be the one my club is holding on 6/29. That will minimize the time spent riding in the dark. I'm a slow rider.