How do I fix stiff dual-pivot brakes? I have Shimano 105 Dual Pivot brakes on my bike. They are pretty old (~7 years), and, although I ride the bike very regularly, I do not use the rear brake much and it has become stiff. (By stiff, I mean that the brake does not fully spring back open when I release the lever.)

Previously when this happened, I took the brake off, cleaned it, and then oiled and adjusted the pivots. I used bike chain oil (wet lube). This worked well, but the brake went stiff again pretty quickly so I'm reluctant to do it again.

Does anyone have any tips for a long lasting repair? Should I be using bike oil? Is it worth fully dismantling them (is this possible/advisable?).
This is a rear case that I would use WD40 or even engine degreaser on a bike part. Remove the pads, drown the brake in one of these and work it till its free. Might be worth removing from bike and soaking in a bath. 

I would no dismatle it unless the above did not work. 

Once the part is moving freely it will have no lube on it. Clean it with hot soapy water, dry it out and use a dry lube rather than a wet lube -  it won't attract the dirt. Alternately use a wet lube but regularly re lube it.