I bought a new serger -- great price -- even though the one I had, probably 25 years old, was a workhorse, but difficult to thread. I did feel guilty because it still worked. Then I used the new one and felt as though I could fly. What a difference! I gave the old one to a friend who was thrilled to get it, so it was also win-win.
With technical things, I hang on to them. My computer crashed two weeks ago, hard drive was unfixable. I had been thinking about getting a laptop to replace the desktop, and aside from the crisis of having to get a new computer, of course the new one is so much better. And that's what I usually find -- the new one is so much better than the old, I shouldn't have waited.