I am debating this issue myself. I was planning to boil down only the first runnings, but now I'm thinking about boiling the first and second runnings together for a few hours. I think it would be easier and I also beleive the beer would benefit from it in that the entire wort would carmelize instead of just the first runnings.
I don't follow this logic here bud.
The idea of boiling down the first gallon is to concentrate the richness. The richest, highest quality wort is the first running.
Unless you mean skipping boiling on the 1st gallon and you mean boiling the entire wort, together, for a longer period. Hard to decipher which you mean.
FWIW, when I made skotrat's recipe, doing the boil down, it was the most malty result I'd ever gotten.