I hit 80k on my 2004 350z. I want to make this Z last forever (hopefully!).

Do you guys have any suggestions on what services to do?

I've done these services at 72k:
Coolant
Air filter
transmission fluid
rear rotor replacement
rear brakes
tires
pcv valve
oil change (77k)

 

Check the belts.
If you have not replaced already,you should have.

 

Run a full trip diagnostic with a data-logging OBDII scanner. Pay attention to your long and short term fuel trims, O2 sensors (both sensors on banks 1 and 2), trottle position sensor, gas pedal position sensor, check for misfires and look for any issues with your RPMs at both cold and hot idle.

You might want to check your brake master cylinder to see if your brake fluid needs to be changed. Also, it's not a bad idea to do a carbon pile load test on your battery to check the condition on that if you haven't changed it already.

Check your bulbs, blinkers, front pads & rotors, ball joints, susupension, bushings (especially the diff bushing). Change your diff fluid. It might be time to think about new spark plugs.

There's a ton of info on every one of these projects on this site. Stretch the jobs out; don't do everything at once. Since this is all more or less preventative maintenance, there's no reason to go out and spend money on parts you don't need just to do it. A good scan and visual inspection is worth its weight in gold. Don't fix what ain't broke.