Long Story (Worth it):
During my adventures I noticed that lairs do not randomise items upon leaving the area.
This led to me asking the DF reddit:
redd.it/eomn8 if they have ever tried to store items in them.
Well I decided to see just how well it works.
AND IT DOES!!!
Lairs (best ones are brides'/bridegrooms') make really nice houses/bases/storage locations.
Anything left in them (blood/bodies/items) stay inside and remain (as far as I know) until you move them.
Quoted from my post:
This is tested with a bridegroom's lair:
New Adventurer: Items Present and unmoved inside lair.
Random Fortress:(not on lair) exited then made a adventurer to check:
ADV died on the way to lair... remaking..
Items are still there!
"Give into starvation" (in lair)
New adventurer. Goes into lair... The last one is dead inside xD all his items sitting on the body.
Conclusion: Works very well!
Advice:
DO NOT KILL INSIDE!
Any blood or items will remain. Drag the monster out first!
Lairs are a safe zone, use it to sleep away from night creatures.
Store extra armor in them for new ADVs!
Making a fortress on a lair:
Items you put there (during ADV) stay inside!
Area becomes a fortress and non-randomisation effect is lost.*
*Im pretty sure... I had some nasty lag near the old fortress and couldn't fully test it
So there you have it. Lairs are now prime real estate! (Given that you clear out the monster)
I just wanted to let others know. I will check back on this often so let me know if you found anything else out!