In my case I doubt it...
usually, as long as there are still siegers on the map (no matter whether visible or not) the fortress is still under siege.
But in my case the siege was luifted as soon as the last goblin left the map, so I am rather sure, that they really fled.
siege tag goes away when the siege leader is killed. or when the goblins get bored. there are still goblins on the map, but no siege tag up top.
i have a habit of scanning the units list immediately after sieges to make sure it's really safe to let the civilians outside.
But as I said, in my case the siege leader was still alive (he was the one who successfully fled [causing the siege tag to go away] and reappeared the next season)
And yes, I for my part also scan the unit list after every siege to find remaining goblins, trolls or ogres
and assess how many enemies my dwarves/traps killed and/or caged
and in this case there wasn´t a single uncaged living goblin/troll/ogre on the unit list
duplicate your save, and check legends. there should be a way to see if this is indeed the same individual as before in legends.
So, I checked my history (an Excel file I made about the history of my fortresses)
as well as the game history.
For one, I was mistaken...
it wasn´t the General who I think appeared twice, but a Spearmaster.
Unfortunately he only led the first attack, while the 2nd attack was led by the general I mentioned.
Sp, what I can prove from game history history is the following:
The spearmaster was the leader of the 1st attack and survived:
1st Attack:
Spearmaster in unit list:
Spearmaster in detail:
In contrast to this, details of a goblin who was killed in the attack:
I can also prove that the siege was de facto lifted, as the 2nd siege contained members of the elven caravan that get killed
(if there still had been a siege, there wouldn´t have been a caravan)
What I cannot prove is, that the spearmaster took part in both sieges, as unfortunately the unit details don´t list all the battles where a person took part and the 2nd attack was led by said general.
I only found one indirect evidence about goblins leaving and probably coming back later:
As we see, the goblins Olngö and Zolak were "created" at the same time (as they are listed directly next to each other)...
I assume as part of an ambusher squad, although I am not sure about it anymore.
The first goblin, Olngö was killed in the spring of 959...
the 2nd goblin, Zolak, however was killed in the late autumn of 960,
that is, 1.5 years later.
So there are 2 possibilities:
1. Zolak was part of an ambusher team that entered the map in the beginning of 959 and remained hidden for 1.,5 years
2. Zolak fled from the 1st ambush (after too many of his friends wehre killed/caged while trying to enter my fortress) and came back later with another ambush squad, which is when he was killed.
While 1. is definitely a possibility, IMHO it is rather improbable, considering the fact that during these 1.5 years there were at least 1 dwarven caravan as a juicy target as well as numerous pets and other animals who freely roamed the map (and who, especially the pets, would have been possible targets for any ambusher team)
Unfortunately my current world with V .25 lists only 3 sieges therefore I wasn´t able to check any more data about recurring goblins
Edit:
Linked smaller pics