Some years ago, I read that a vehicle will cost you about $400 a year in maintenance, some years you wouldn't really spend much at all, some years you might have to shell out $800 for a major ticket repair.
So a new vehicle with warranty will get you out of most of that expense for several years, but sooner or later, it's going to catch up with you. If you trade often, then depreciation on your trade-ins will get get you.
I like to think that by keeping what I've got, I don't have monthly payments. I really like my current truck and even though I just went through one of those years where I had some major stuff to work on, I had a four year period before that in which I had no expenses on it other than lubricants and gasoline. Not having monthly payments allows me to keep that money in the bank, so when one of the big failures hit, it's no problem to draw the money out and get the parts.
I do 85% of the repairs myself, so there's a large savings on repairs. And I'm getting up in the age where I may not outlive the payments on a new truck, so I think I'll just hang on to it.
All said, I think financially, I'm coming out ahead, I just don't get to smell the new car smell and drive around in a shiny new truck, but I use my truck, so even a new one wouldn't look shiny for long.