It hasn't been framed long enough to have any kind of
serious effect from the gasses that the paints give off. (Or
even any kind of gas buildup at all.) The real danger from
the gasses given off by the paints is damage to the cel, not
expansion of the gas bending the cel inside the frame. The
glue on the corners is still holding just fine. There is
no glue between the spacer and either the mat or the backing.

(Incidentally, where/why would you use glue on the spacer?)

Many Sharp Smiles,
--Drac