I had 3 of the 7.3's and put a fair amount of mileage on all of them. The only issue I ever had was 1 crank position sensor went bad and was intermittent so it didn't strand me.
If you ever do have to go into the motor, I would consider replacing the injectors. Not because you think they are bad, but because there are high quality after market units available that will give you better power, better economy and will outlive OEM. If you put a set in you can forget about them for a long, long time.
Randy Rosetta KDØKWX TLCA #19351 NOW 2015 Rubicon Hard Rock & (2) 1970 Boss 302 Mustang's THEN 69 FJ40 Buggy "Meanie", Mini-truck "Gecko" & 74 FJ40 "Blue Mule"