Just thought I would pass along something that might help some folks. I did the D1 wiper arm on D2 swap this evening and after I was done I brought the old wiper arms in and checked them. I found that the pivot point near the where the arm attaches to the lug(?) was very stiff. I put some lube on the pivot points and worked it a little, in a relatively short time I felt it loosening up and the spring tension increasing. I have read on other posts about springs wearing out and I have doubts about that, the springs are pretty stout and they don't get stretched much.
I broke the blade locking mechanism on the D2 arm trying to break ice off of it and I now have the D1 arms on so I'm not going to test my theory, but I strongly suspect that lubing and working the pivot points to free them up would fix a lot of these problems. I used Tri-Flow for the lube because it doesn't congeal in cold weather.
All that being said I think I am glad I did the swap, no plastic parts on the D1 arms to break in the cold and wiper blades will be readily available.

 

 

If the pivot points are binding some sort of light oil would work best to free them up. Maybe after they are freed up something like a light grease would keep them free and last longer.
I'm not much a fan of WD-40 for a lubricant but it would probably do alright for freeing up sticky pivot points, 3 in one oil might work as well, a penetrating oil might be even better.
I just did a quick search and found that white lithium grease is good down to about 0 deg F, so I would think it would be good to keep the pivot points free if the temps don't go below that.