TL;DR: If it's not cached, does it really matter if it's offline for some time?
Long version:
If you're so popular all around that you really really want a very very short TTL, people will query all the time from all the places that "count", won't they? So it's gonna be cached.
If you're not so popular or not all around, what does it matter even if you had a very very short TTL? You're not loosing much.
