The dungeon being synced or unsynced makes no difference in terms of server load.
Think of it as like, bathroom stalls or karaoke rooms or some other type of set-amount resource that a person or people can enter and then lock. If enough people do so, waiting happens. We already see it some of the time when a duty finder party is filled, but the window says "reserving instance." That means there are no available instances to enter. All the rooms are full/taken.
In the current setup (which is unlikely to change), there are safety checks in place to make sure that an instance not in use is added back into the list of available ones. Without those checks, a group (perhaps a large group because it's per-data center) could theoretically block all instances, which would require Square Enix to forcibly remove the players by manually kicking them out. (Server restarts / emergency maintenance).
But it doesn't even need to be actual people. Bots can and do do this already in a variety of other services. (In my line of work with event ticketing, we have have to block bots from grabbing all of our reserved seat tickets. Or nobody gets to go to their concert or sports game if it's popular. Assuming SE has some form of NOC, they probably get alerts when a certain threshold of content is "locked" in use.
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So yes, it's not a big deal for a single player or a group who want to go in, take some screenshots and head out. But imagine if you had a 6 hour RP scene in Sastasha, or in a high-end raid. The 90/120 minute "maximum instance time" limits are there to not only send an inactive character back to their home world, but to also maintain good server health.
Think of it as like, bathroom stalls or karaoke rooms or some other type of set-amount resource that a person or people can enter and then lock. If enough people do so, waiting happens. We already see it some of the time when a duty finder party is filled, but the window says "reserving instance." That means there are no available instances to enter. All the rooms are full/taken.
In the current setup (which is unlikely to change), there are safety checks in place to make sure that an instance not in use is added back into the list of available ones. Without those checks, a group (perhaps a large group because it's per-data center) could theoretically block all instances, which would require Square Enix to forcibly remove the players by manually kicking them out. (Server restarts / emergency maintenance).
But it doesn't even need to be actual people. Bots can and do do this already in a variety of other services. (In my line of work with event ticketing, we have have to block bots from grabbing all of our reserved seat tickets. Or nobody gets to go to their concert or sports game if it's popular. Assuming SE has some form of NOC, they probably get alerts when a certain threshold of content is "locked" in use.
--
So yes, it's not a big deal for a single player or a group who want to go in, take some screenshots and head out. But imagine if you had a 6 hour RP scene in Sastasha, or in a high-end raid. The 90/120 minute "maximum instance time" limits are there to not only send an inactive character back to their home world, but to also maintain good server health.
