Tough road or touring frame/bike I recently had my bike destroyed by a car. I love cycling, and since I'm no longer a research fellow, I'm considering replacing it with a bike with great longevity (N.B. I know that until a process is perfected for constructing self-healing, Adamantium bike frames, no bike is guaranteed to survive a collision with a car). I've owned several aluminum- and steel-framed bikes in the past, and liked them all (although aluminum Canondale and GT frames had fairly thin, oversized tubes and once or twice got dinged on university bike racks, and the steel bikes slowly succumbed to rust in the rain/snow/salt of winter). 

For these reasons, I've long held titanium frames in high regard, because I've heard anecdotally that a good titanium bike can last the longest with minimal care (i.e. it is strong and resists corrosion); however, I recently read about stainless steel frames (e.g. KVA and Reynolds 953), which are very strong and corrosion resistant (although I've heard conflicting accounts as to whether stainless is as corrosion resistant as titanium). 

Which is the frame material with greatest longevity-- stainless steel or titanium? I've learned that in addition, there are other stainless steel frame types such as the nascent Reynolds 921 (Also, do you know the manufacturer with greatest longevity? I've read that the longevity of the frame not only depends on the material, but depends even more so on the quality of construction, and it's almost certainly better to have a good aluminum bike than a titanium bike held together by gum.) And if stainless is the best, is there a recommendation between KVA and Reynolds options? I found a couple of nice tables comparing physical properties online, but wanted to ask because such tables does not quantify corrosion resistance or the average tube thickness used for that material or the difficulty working with the material (which can manifest itself in greater likelihood of imperfections and later cracks), or any other je ne sais quoi that a bike expert like you can recommend. 

Thanks for any help you can offer, and hope all is well with you and your bike.
Its not just the material that affects frame longevity, but the design of frames - different tubing thicknesses and geometries will last longer than others given the same materials. 

That being said, a lot of touring bikes (often made of steel such as Reynolds 521 or the Tange equivalent or something, since in a pinch, you can repair steel in pretty much any country and its "ride quality") are essentially bomb-proof if you take care of them [the material is a neglectable factor relative to this, especially since you won't build identical bikes with different materials due to different material strengths and properties]. Some people have hundreds of thousands of miles on them with little degradation. Examples of touring bikes are things like Surly Long Haul Trucker, Trek 520, etc.

That being said, a lot of 70s Schwinns and 80s road bikes and what not are still running perfectly fine after replacing consumable parts (chainrings, chains cassettes, hub repackings, bottom brackets, etc.) when they were maintained reasonably. 

Part of the reason why titanium lasts so long is that the people who buy titanium bikes are already extremely invested in their bicycles and take extremely good care of them. They aren't left outside, they get the top level of care, they don't abuse it, etc. so they see a very nice environment. 

Also, very few if any decent bikes are going to survive taking a significant hit from a car.