Toyota them selves list the Prius's live expectancy at 100k miles. this is a little scary, but batteries and electrical motor wear are the big limiting factors. The average car starter goes out around 100-150k miles, and that is a smaller, more simple version of what’s on the Prius... An Electric Motor that turns mechanical parts.

If you are realy for saving the environment, you would look at things like how much energy it takes to recycle. There is a reason they are willing to pay you for aluminum and not for paper or plastic after all, because it takes less energy to recycle aluminum then it does to dig out and process the bauxite into aluminum... hence, they pay you for their savings in energy. Paper, plastic, and most things people recycle, uses more energy to recycle then it saves.

Also, if you were REALY REALY for saving the environment, you would not buy a hybrid at all. what you would do would be perhaps, buy a a Salvaged automobile and repair it? instead of re-processing the material for a huge energy loss, you would Re-Use the entire thing. In one action, you would do more for the environment then you could ever do with a lifetime of recycling Aluminum cans (the one thing that takes less energy to recycle remember).

Or perhaps instead of spending 20k on a Prius, you would spend 5k on a used economy car, and spend 15k in a donation to an environmental organization... which I don't believe is a good choice, looking at the sizes of most of their "non profit" headquarters...

bottom line, you actually have to think for your self when it comes to doing good for the environment. I have several cars...

01 Pontiac Trans Am with 350 wheel horse power (which believe it or not, kids, is an Ultra Low Emissions Vehicle. Look it up.)
95 Chevy Tahoe (with 290k miles, doesn't burn any oil)
04 Pontiac Grand Prix Supercharged
99 Dodge Neon (purchased the shell of the car on its way to be crushed, and am rebuilding it using parts from other cars)
93 Chevy Cavalier (purchased with engine problems, the owner was going to junk it. Its running fine now)

So, you can see, even though I own alot of vehicles that burn a reasonable amount of dead dinos (the trans am gets about 16mpg the way I drive it) There is far more to think about when it comes to the Environment then just how much gas it uses...

Otherwise you are like one of those suckers who thinks CO2 is the primary greenhouse gas. (Water Vapor accounts for about 80% of the greenhouse effect, yet some think hydrogen cars that exhaust nothing but "harmless water vapor are grand). You need to look this stuff up for your selves... and don't be so quick to claim "oh, they are just a stooge for the automotive industry" or "big oil." Otherwise, every time someone brings out something published by an environmental group, you need to point out that group's extreme Bias as well. its best to look at all the data and come up with your own conclusion, not to ignore data because you don't like what it says.

so, perhaps you should look at purchasing a salvaged Chevy Tahoe instead of that brand new Prius next time eh?