Probably I am rationalizing but the DTB was more of a checkpoint that a major goal. The goal is the Eastern Mountain ride in September.
But this is all defeatist talking. It is still three training weeks away and I am in excellent shape. I just haven't proven to myself I can do a 10-12 hour ride and recover enough to do it again next day. And given the time left and the need to be careful about how hard I push, I won't know until I am on the route.
Training week summary: Total Training 39:30 hrs, 256 miles, Total Climb=13,500', TSS=742, and KCal=7300.