Synonyms for Staleness:

n.

cognition (noun)
triteness.
dullness (noun)
flatness, vapidity, insipidity.
innocuousness (noun)
blandness.
insipidity (noun)
mildness.
staleness (noun)
triteness.
tastelessness (noun)
flatness, blandness, insipidity, plainness, mildness, banality, vapidity, tastelessness, weakness, unsavoriness.

Other synonyms:

Other relevant words:
triteness.