Ooh, first time posting here and got some stuff to share about it.
Retiring works quite okay, !fun! stuff happen when you unretire though.
If you made a trap/farm with an untrained wild animal(Giant cave spider, dragons etc ) that guy will be placed somewhere random when you unretire and if they are caged, they'll likely be badly trained and loose somewhere random. I ended up with some named creature corpses and half the fortress melted that way before I figured that out. Butcher them or wall them off somewhere before retiring ( they were released but still contained ). Caged invaders disappeared for me ( had a bunch of them in stockpiles with 3 of them built in beastiary, all of them were gone upon unretiring )
If you have a monarch, monarch may decide to go back to the original mountainhome. Mine did , took her artifact bed from her room with her. She was in her royal guard military squad ( Martial art training good mood purposes ) and thus she was bugged on the military screen, stuck as 'traveling'.
Your artifact list gets bugged/reset upon retiring. I don't know how that works, I had several pages long artifacts/books in the menu, but when I unretired the list was more or less gone. I did check where they were stored ( guildhalls / museum ) and there wasn't any empty pedestals so I'm assuming they were still there, just not on the list.
Any chests you placed in dwarf bedrooms will be removed and hauled to storage, it may be keeping cabinets, I'm not sure, program generated forts seem to have cabinets in them so they may stay. Armor stands/weapon racks get hauled also I think.
The booze/food stored in fort seems to still be there when you go there with an adventurer, I stocked many adventurers by sneaking in and grabbing some quality grub that way. When you unretire though, almost all your booze will be gone.
Your favorite dwarves may get a barony and leave the fort. I ran into one of the war heroes in the original mountainhome and she was marked as a baroness. Her husband was still in the fort I retired.
When you unretire, it will seem bugged for a while due to LOADS of hauling jobs present. Gets better in time.
If you used quantum stockpiles, they may or may not need re - building. Stockpiles keep their proper settings, minecarts are hauled away, tracks are present. Sometimes they work properly once you put back the minecarts, sometimes you need remove tracks, rebuild tracks and create a new hauling route.( It could also be that they are in a low priority because of the LOADS of hauling jobs )
May keep posting more about it. I accidentally embarked with a dying civilization and doing a lot of retiring/unretiring, adventuring/ legends browsing atm.
Edit: Spoiler part grammar was even worse than it is right now.
( I chose it because I liked the name ) which only had the mountainhome, and also embarked outside it's borders ( no baronies/economically linked sites in 70 years of play in two different forts, can't start an adventurer from the civilization ), planning to train a robust military, retire and start several outposts in between my current embark and mountainhome ( mess with ini to stop migrants after the first two waves ) hopefully reviving the civilization ( interesting setting, civilization has a very old queen with her husband dead over a hundred years ago, no heir, mayor of the mountainhome is a necromancer and there's actually a story there. Captain of the guard in mountainhome is a notorious womanizer, a serial dater/divorcer then, finds the 'one', stays with same partner for a long time, partner dies, gets corrupted by the mayor, goes to steal a necromancer slab for mayor, mayor becomes a necromancer, then there is a brief love affair between the captain and mayor which leads to... captain also becoming a necromancer. I'm assuming they will make a power grab soon as queen is dead. Trying to keep her ass put in the outpost colonies in savage wilds, where the biggest problem is giant vultures scattering caravans with the occasional goblin sieges... also the ruins of another dying dwarven civilization after they dug too deep. I did try to raze the site once, ended up 10 dwarves meeting very graphic demises and more than half of the initial 80 strong raiding force ( almost all legendary ) being imprisoned. There are some nasty demons there instagibbing any adventurer I send from one screen away...