I drove across Canada ~4500km (2800 miles) last July. I have about 150k miles on my car too. You'll be fine, just make sure the car is up to date with the maintenance and nothing is making noise or shaking.Anyone ever driven their is300 across country? I'm thinking of doing it once all parts get installed. Ny to California. Car has 160K on it.
Update: Car feels amazing. You can really feel the difference with the headers and lighter wheels, not to mention how much better it handles with the coils and front/rear sways. Made it from NYC to LA no problem at all! Utah and Colorado had some beautiful roads, only got one speeding ticket (98 in a 75, $240!). I actually quite like the exposed center caps, it give a functional feel as if I'm changing my wheels so often that I cant bother with center caps lol. Now I'm dying for more power under the hood!Nice to see you went through with refreshing your car instead of jumping ship to a Subie, M3, or other money sink. Im personally parting out my WRX, and picked up an IS300 because of how much better the IS300 feels. In the same boat with refreshing the IS as the previous owners didn't appear to be enthusiasts, so this implies years of cheap gas, bad oil, and under appreciation (warped rotors, uneven tire wear, and very dirty throttle body from excessive blow-by).
You made a great choice in revamping her! The IS is a much better car than a Turbo Subaru.
On my subaru when I had RPF1s, and didn't want to spend $120 on enkei center caps. You can buy Honda Odyssey center caps, sand them down to a uniform level (so the logo doesn't shine through), and coat them in a nice matte silver enamel.