When do you throw in the towel?

I took care of my 2003 Silverado 1/2 ton, but at 185K and never having done much more than change the oil and a few regular maintenance things we decided that it might become a time bomb. The steering box was starting to leak, so decided we needed to replace instead of repair. It could have gone another 100k without any major issues or it might have failed the next week. Hard to say. However, we were in need of an upgrade to a larger vehicle, so it all worked out. Eventually all vehicles need some major repair or tuneups eventually. That's the price of vehicle ownership. Good luck with your decision. Either way it'll cost $, but as long as you're happy with it, that's the right one.