Here is something you definitely don’t want to happen in mid-winter: your furnace suddenly fails on you. And not only fails, it dies. The sort of breakdown that the furnace can’t come back from. You’ll be stuck having to purchase a new one.
No matter what you might imagine or what someone else may tell you, this shouldn’t be the way your current furnace ends. You shouldn’t run it until it collapses. That’s both wasteful and potentially unsafe. Instead, watch for the indications your furnace is getting too old to keep. Getting ahead of the problem and having a timely furnace replacement is the best way to move on with your home heating.