GAS can be tamed, somewhat, by a requirement that one must "master" the most recently purchased item. It can also be tamed, somewhat, by a massive case of "wait and see what comes out next" (that's me!). I keep waiting for the 7D2. I was waiting for the Sigma 50 f/1.4 Art, now it is on perpetual back-order, why not just wait until the possible photokina Canon releases?
Finally, GAS can be tamed by a competing GAS, in my case, camping and fitness gear.