Personally, I'd save the slowdowns for Rescue. As eastx's article points out, it's notably harder than the Run chapter. It's not impossible - I've made it about 10 levels so far - but in terms of getting it in one go... yikes.
One other thing I noticed with the update - the random sections that appear in Endless Run have been added to. So, if you were trying to get to 50k points and learning the sections, you may want to hold off on the update until you break 50k.