The water temperature has little to do with trolling speed. Depth and speed control accomplishes only one thing. To keep your lure "ticking" the bottom contours and staying in the strike zone of the target species. To that end, you would go faster the shallower you are and slower the deeper you are; in order to maintain this critical bottom contact when trolling. Obviously, other factors come into play here as well, such as line diameter, the amount of line let out, the size/style of the lure you are presenting, etc..
I don't care how cold it is. Maintaining bottom contact is paramount. Randomly "S" trolling open water is not only less effective, but it is can reduce your catch ratio considerably. Bass are normally a bottom feeding/living species. Rarely do they suspend. And when they do, it is not for long periods of time and usually within close proximity to structure (defined as bottom contours....NOT trees!)
Yeah, I know when the water cools you're suppose to slow down. But you are not looking for a "bite" here, if you elect to troll. You are looking for a reaction strike. Two quite different animals. You cannot move your lure fast enough for a bass not to catch it (within reason of course), regardless of the season, if he is triggered to do so. So don't worry about that as much as keeping your lure on/near structure.
My apologies for rambling on.