I hear you on the appeal of shorter rides. I'm thinking my randonneur days may be behind me, though I do like the full-body work out that a 8-9 hour ride provides.
The geometry on your bike must be really relaxed to do those sort of hours. Not to mention a top notch comfy seat and extra padded shorts (with chamois cream?). Do you have several cafe stops during the rides to fuel up the body and loosen those muscles back up too?
Honestly, I can't imagine being in the saddle for that length of time, kudos to you.