I have also learned to define your goal in rando and then build the rando bike to suit your goal.

I've done Brevets on a Touring bike and the weight at the end of the ride is noticeable if you want to have a fast time.
I've done Brevets on a relaxed road frame but it has limited carrying capacity and doesn't do fenders. I've done fast comfortable brevets on that bike but only in the warm and dry summer months.
I've done Brevets on a Brevet bike (Raleigh Clubman) and I am comfortable over long distances in the heat, cold, and rain. However, everytime I show up on the Brevet bike the other guys are there on their road bikes and I die trying to keep up as they accelerate up hill on bikes that are 10lbs lighter.

My current plan is to do warm 200k-300k brevets on the relaxed road frame (Schwinn Le Tour Alloy with Ouza fork) and long brevets 400k+ on the Clubman and force myself to not worry about trying to ride as fast as possible (easier said than done for me).

So, what goal do you have in mind for your Rando build? Speed over comfort or comfort and storage over speed? It is my opinion that Speed, Comfort, and Storage are the three legs of the stool you have to balance in building a Brevet bike.