Playing one card a time very slowly. Not because of thinking or anything. For instance, once he gets down to his coins he will play one at a time.
Didn't start that way. Started going a little more slowly for about a turn or two around 12 or 13 I think, by 15 was intentionally taking as much time as possible. At this point I will probably play it out because there are 4 provinces left and I will get 2 per turn, but this is still annoying.