I was in the same boat as PRISM99, I started collecting and could not stop. Then it dawned on me that I could never use all of them unless I devoted a project to each one, and then I'd have a dozen projects going at the same time, which seemed pretty unrealistic. And I hated not using them, seemed a crime to let a perfectly good machine that worked well just sit there unused.
So...started listing them on Craigslist for sale. I'm down to my last one for sale now, I asked what I had paid for them and recouped my investment on all of them.
Of course I'm not totally cured. I'm still on the lookout for the machine that I used when I was a kid, it was a 1940's Kenmore and probably the one possession my mom cherished the most. I just want to have one for sentimental reasons. I've seen quite a few but I want one in good working condition so still looking.
I too see machines at garage sales and thrift stores all the time and am "haunted" by them, but I know the feeling will pass in time. Sigh.