Interesting and informative discussion. FWIW, my first vacuum cleaner was completely dead, no funny noises, no slowing down, or such. Suddenly one day, it quit.
I think Charley and Scott might have diagnosed what happened and have the answer. The problem is that I can get perfectly good used Oreck vacuum cleaners of the type I am using off eBay for around $25 and it is cheaper to just replace the vacuum cleaner as needed. That leaves more $ for other scrolling toys/tools, wood, patterns, etc.