Acetates are generally unstable unless in solution. They are one of the worst salts.
Also DMT acetate is a sticky goo just like DMT HCl, DMT citrate, DMT tartrate, DMT ascorbate, etc. Only DMT fumarate is a dry powder. I don't know of any other dry salt forms of DMT. For stability you want to make DMT fumarate using fumaric acid. For long term storage purposes, fumarates are said to be the most stable of all the salts.
When DMT acetate breaks down, it should break down into freebase DMT and acetic acid and the acetic acid should evaporate away. At least that’s known to happen for many other acetate salts, especially if stored in excessive heat.