Windows won't stay open
You are totally right about them being called 'spiral balances' and they are notorious for failing. When I was doing replacement windows here in Florida, one of the main reasons customers were replacing windows was for that very problem. I was not in the business of repairing windows, so I do not know if there is a good or inexpensive fix. I do know that many of Window World's customers bought from us due to the fact that they could get a window replaced for little more than having a window repaired and get a lifetime warranty. But look around, call around. See what you can find in your area. If nothing but the balance is bad, there might be a good way to have it fixed. If the window itself is not all that good, consider having it(or all of them) replaced with a better quality window. You can save money on heating and cooling, plus add value to your home. There are many great windows/window companies out there. Just do a little research and get some quotes. Just make sure you are comparing apples to apples, oranges to oranges.
Do a search on replacement windows and you will find a plethora of information about the subject. If you decide to get replacement windows, get at LEAST 3 quotes. Prices will vary by thousands of dollars. Sometimes even on the same brand. Going with a nationwide company is definitely best, especially in this economy where a local company might not be there tomorrow, but a national company will almost always take over warranty/customer service even if a local franchise should fail. This often applies to all types of home renovation.
The problem I have seen with spiral balances is that even though they might be well lubed and/or even stainless steel, is that they are often attached to the window with non-stainless or pot-iron, and that is where they fail.
Man of many hats