1) Agelessness 2) Immutability 3) Immutableness 4) Quiescence 5) Setness 6) Unalterability 1) Fastness 2) Fixedness 3) Fixture 4) Immovability 5) Immovableness 6) Permanence 7) Secureness 8) Stability 9) Stable quality 10) Steadiness 
fixed state; stability; permanence
• (n.) Coherence of parts. • (n.) Fixedness; as, fixity of tenure; also, that which is fixed.
Fix'i·ty (-ĭ*tȳ) noun [ Confer French fixité .] 1. Fixedness; as, fixity of tenure; also, that which is fixed. 2. Coherence of parts. Sir I. Newton. 
The USS Fixity was an American Admirable Class minesweeper of 625 tons displacement launched in 1944. The USS Fixity was powered by diesel engines providing a top speed of 14.5 knots and carried a complement of 104. She was armed with one 3 inch dual-purpose gun and four 40 mm anti-aircraft guns.
fixity 1. The quality or state of being fixed and unchanging. 2. Something that is unchanging. 3. Something which is fixed or immovable.
the state or quality of being fixed; stability; permanence. · something fixed, stable, or permanent.