Not just GAS, but I am trying real hard to keep a lid on AS in general--"Acquisition Syndrome" with regards to "stuff" of all sorts.
I've mentioned this on here so many times I imagine people are sick of it, but a flood claimed about 98% of everything my family owned a little over 4 years ago.
It's amazing (and alarming) how quickly "stuff" re-accumulates. I have a family of four, so there will always be a ton of "stuff."
But losing things to that flood--and I lost every book, movie, comic book, CD and piece of music gear (except for one guitar I happened to have with me) that I owned. It made me realize it IS just "stuff." The things we lost that hurt the most are family photos, drawings my kids did, love letters between me and my wife...
Before I buy almost anything these days, I seriously consider how much I want/need it (nearly everything, of course, is a "want" and not a "need.") Will I still listen to this album or watch this DVD years from now? How often will I refer to this book?
I still like my stuff and have a small, tight collection of books on subjects of interest to me, I have re-built (on a far smaller scale) some of my film collection, I have plenty of music to listen to, and I have plenty of instruments to play (one acoustic guitar, one electric, and two basses.)
The only "thing" I feel like I could use is a real bass amp. Little practice amp for the guitar is fine, but I hope to get back to jamming/playing with other people and (hopefully) even gigging again. That won't be possible with my 35 watt practice bass amp.
Unless something completely comes apart and is irreparable, or something gets stolen, catches fire, etc. I doubt I'll ever buy another instrument, as much as I do long for certain basses (ahem...if anyone wants to donate a Ric 4001 or 4003, or maybe an Ovation Magnum I to me, hint hint...)
Minimalism isn't for everyone, and I certainly don't look down or roll my eyes at people who own 50 basses. That's cool for them and I am sincerely happy for them. Basses are cool! I dig seeing people's big collections and NBDs.
But for me, I do believe that in a sense your possessions possess you.
For me personally, back when I DID own a dozen guitars, multiple basses, all manner of pedals and amp gear, etc. I sort of felt like a slave to it all. Worrying about proper storage, regular maintenance, keeping things in playing rotation, keeping things strung and playable, the space it all took up, etc., etc.
For me it became more of a chore than a pleasure just owning that much.