 Just because a window is fogged, which often happens as those panes wear, it doesn't mean it has to be replaced. Yes, it's not cosmetically very pleasant to always look like it's a foggy day outside when you look through it. Sometimes you'll see some staining. It will be slightly less efficient, but it's totally cosmetic for the most part. So if you can live with it, you're going to save a whole lot of money.