Kind of like getting a computer. When you walk out the door with it, it becomes obsolete. If it ain't broke do fix it. You said it in your 3rd and 4th sentences. You know how your machine works now but don't know how the new one will work or for how long. Trade-in isn't great but price is right. I would stay with what I've got and save the money for when you will really need a new one. If you love the one you're with why new?