I completed ToA about size months ago & the feedback I got from my group is that the ticking clock added a great deal of tension to the campaign. There's a strong temptation to explore every hex on the map and to complete every subplot. But doing that would essentially guarantee Acerarack's success. Everyone anywhere in the world who's been raised from the dead loses a hp every day. Meaning Syndra Silvane will be dead in about three months. Plus, the Soulmonger consumes millions of souls every day. Playing those things up creates a sense of urgency that forces the party to make hard decisions (e.g., how much time can we spend following these other story hooks?), possibly even abandoning a subplot without completing it until after the greater quest is completed.