I used to use two papers, and yes it does make the joint harsher and takes away from the weed taste. Two papers might make it burn slower, but only because it will be tighter because you have more paper and because of that, more control. If you can roll a tight joint with one paper, do it. If you can't, use two. I use a rolling machine because my hand-rolled joints are shit.

edit: oops, old thread. I'm sure the joints are already rolled and smoked.