The rules are sufficiently (and, I think, deliberately) ambiguous in this matter that I don't think there's much to be said from an official perspective.
Personally, I feel that Exalted's "no backsies" principle is best supported here by permanently terminating workings anchored to things that die. Put a working on the land where a city is built, and it will linger even if the city is destroyed, but if the city grows the working will not spread with it; put the working on the city itself and it will grow with the city, but if the city is razed and its people put to the sword, the working is permanently ended, no matter if a new city is raised amid the ruins.
Also, I think it's hard to argue that there have been so many sorcerous workings that you literally can't pick out the active ones from the layers upon layers of old ones. AESS explicitly lets you analyze the functions of workings you see. Even if having a lot of them piled up makes them more difficult to study — which is not inherent to the concept — your character has Occult 5 and can figure these things out. And your Storyteller's ruling pretty much means that putting up worldwide Solar 3 workings would render AESS useless to everyone, which seems counterproductive.
(If you have access to Roger Zelazny's The Changing Land, it has some very good examples of how All-Encompassing Sorcerer's Sight might function on an in-fiction level.)
Also note that while it's theoretically possible in your game that each Direction might still have a handful of high-end Solar workings on it — though as Morangias said, some workings might require maintenance whose absence has caused them to lapse, or be tied to subtle factors rendered invalid by the turning of the Age — it's ridiculous to think that every field has a working on it. There have never been that many sorcerers, and even thousands of city-sized workings would be effectively invisible on the Creation map due to differences in scale.
Originally posted by Ghosthead
I like the idea that Workings are generally present, but quiescent; they were tied to the proper performance of rituals, and geomantic energies and such, which are lacking or misaligned. That said, also OK with them being tied to points of reference which they cannot survive beyond. Some may have been deliberately limited in their temporal scope, to diminish their scale (as their architects would've have planned to renew them in future).
While such things might be deliberate, they may also be the result of the same sorts of fundamental limitations faced by real-world engineers. Mechanically, these would typically manifest in low-Finesse Workings or as a result of botches. As such, they are likely to be common.
Remember that (barring certain edge-case shenanigans) Terrestrial workings can affect a region no larger than a village, and Celestial workings can affect a region no larger than a town.
So, on the permanency of workings. The corebook makes some pretty strong statements about their durability. Here's a couple big exceptions
1. The working is, by its nature, temporary. If you brew a potion that turns someone into a cat-headed ogre for three days, it's only going to last for three days.
2. Sorcerous weirdness says so. When the player and the Storyteller work out the mechanics of the working based on Finesse, "when is this going to end?" and "is it gonna break down and get weird down the road?" are valid considerations to discuss. Botches can also add complications that take on this form.
3. The sorcerer builds an end-condition into the working. This can potentially overlap with both of the above categories. Why would you do this? Because once the working expires it becomes narratively irrelevant, and you get the XP you invested in it back. Frugal!