200,000 is a huge milestone for cars. I think he was just trying to sell you the car. It's using the same 6 cylinder engine that has done Nissan well in other models. Based on other Nissan models, if regular service is maintained you should see the car last you into the 100,000 mile range.
oh no.. that v6 is great.. i have a 99 maxima with 203k miles on it.. i still bring it in for service every now and then .. but.. it runs smooth .. it runs very nice.. i'm not sure if its the same type of engine as the murano all i know is that maxima was built in japan and not the U.S .. but im sure I AM 100% sure the murano will last you at least.. at leat 150.000 miles if you do things right.. and by doing things right i mean staying on top of your scheduled maintance..
and believe me.. unless you drive 1.000 miles a day.. you dont want ur murano to last you 700.000 miles.. it would just be... too old..
I bought my 2006 Murano brand new, and all I did was change the oil on time per the car manual. It's got over 224,000 miles now, and it still runs great and is very comfy to drive. Only complaint is that prices for parts seem high when something does break.