Wonderful insight... I can certainly relate and when it comes to GAS I try and hold myself to a simple rule.
1.) with the exception of certain breeds, do not approach photographic equipment as an investment. An investment must have the prospect of a return, and unless you purchase something at a complete basement level price you'll likely never see a return unless you're shopping out Leica/Zeiss (Zeiss to a slightly lesser degree).
2.) never repeat formats.... unless you have a distinct strategy (like 2 35mm bodies with different focal lengths for faster shooting). I love different formats but I only need one MF, one 4x5, one 8x10, etc etc etc.
3.) After your initial major purchases I try and play in the black. It's tough to incur up front costs but if you can recover most of your cost at a later date it's nice to either upgrade or add elements with that recovered money.
4.) Last but not least, I try and never sell off a piece of photographic equipment just to pay something off, like a bill or some debt. I like to constantly remind myself that photography is a true passion in my life, I would much rather make sacrifices in other areas of my life (such as avoidable expenses as luxury cars, expensive restaurants, clothing etc etc) if it allows me to keep on buying film, lenses, chemistry, plates etc etc etc.
