Its anyone guess.I would say If you off road it alot chances are it gonna happen sooner than later Lol...Out of the last 5 Superdutys I have had.It was my 04 that had one going at close to 50,000.You will usally get alot of road noise or rumbling type sound when they are startin to go.If your suspicious of a Noise, jack up the front wheel check it for play or give it a spin and if its going you will usually be able to tell.Almost every manufacturer uses thes Unit bearings anymore so it aint just Ford that has issues.As far as Issues with the 04 MY.There were alot of Engine updates done from 03 MY.I myself had a real good 04 with Minimal issues,A EGR valve and a Reflash plus the L/front wheel bearing was startin go when I traded it off It had 51,000 on it with quite a few heavy towing miles since new.And it Never had a programmer on it just a exhaust