Typically, I speed up buildings that unlock characters I like, because I want to play with them ASAP. I will speed up a few tasks if I'm really bored and want to get along in the progression. So, I speed up more stuff than the perfect "patient" version of my self would, but I'm imperfect and have no problems using what I have when the time arises. I think I spent 20 donuts speeding things up on this update. I didn't speed up any of the buildings (Escalator and Popsicle just finished!!!), but sped up a couple challenges because I was bored and wanted to see where the quest progression led while I still had all my characters free. (I kind of suck to shop for, so I got a lot of iTunes cards for XMAS. Thus, I have plenty of donuts to use, but I'm pretty restrained in their usage on speed ups.)