I've got 80,000 miles on my 2000 V10. No problems and runs fine. I did, very carefully, replace the spark plugs at 40,000 miles (there are a lot of wrong ways to do that and one best way). I rechecked the plug torque 20,000 miles later, and they were all fine. The 2002 and later V10's had changes and the 2006 and later had another 50 hp and a 5th gear added to the transmission.
From an old post of mine:
From what I learned on the Ford V10 Forum the proper torque was 168 IN-lbs with high temp never-seize on the threads.
Better to remove the plugs, but that has to be done carefully to avoid problems. Here's how I did it.
1. Remove the coil-on-plug coils and blow out the spark plug wells with compressed air.
2. Squirt in WD40 or PB Blaster and LET SET OVERNIGHT (or at least an hour).
3. Loosen the plugs just 1/8 to 1/4 turn!!! NO MORE.
4. Squirt more WD40/PB Blaster into the well and LET SET OVERNIGHT.
5. Remove the plugs and check the threads in the head with a bright pencil light.
6. Check/replace the plugs (be sure gap is correct----which I think was around 0.055").
7. Place a LITTLE high temp never-seize on the plug threads. Be sure none gets on the spark plug tip!!!
8. Hand start the plugs (a spark plug socket with a rubber insert and a 6" extension is a big help). The plugs should screw in easily until their shoulder bottoms in the head.
9. Torque to exactly 168 IN-lbs (14 ft-lbs).
10 Recheck the plugs after 5,000-10,000 miles (and maybe every 25,000 miles thereafter to be safe).
If all else fails (or you want an insurance policy when traveling), buy a Timesert Kit