Every time this comes up, I always think of the Disney Channel show Phineas & Ferb.
Namely, the special episode "Summer Belongs to You."
@MWollaeger's post makes me think of that episode even more so, as it describes it almost exactly.
The kids intend on chasing the sun over the summer solstice to create "the longest day ever". And, as would be expected, they nearly don't make it. They get stranded on an island in the middle of the ocean as the sun sets. The way the episode is drawn out, I feel it so clearly indicates how a sunset is a Spacelock, especially since the sunset limit and other elements of dwindling options support each other in the story, instead of stepping on one another.
Also, there's even a character who exclaims at the beginning that there are "exactly 24 hours in the day and that's it. You can't change that." Obviously, it being Disney, they succeed and manage to beat the sun. In effect, this means that they change the amount of time the sunset represents, and however long that might have been doesn't matter so much, only that keep up with the spatial traversal
Even though there is a theoretical time limit against the story, it doesn't matter. Given the requirements and limitations within the story, as presented, time is extremely malleable. (Though, by any external indication otherwise, it "shouldn't" be.)
At the highest level, that would seem to be the purpose of Timelock vs Spacelock. Even the names of the dynamics suggest the idea: It would seem that choosing one as rigid (that is, locked) frees the other, in that particular story.