I have an 2004 f150 2wd with the 4r75w tow package. Bought from a buddy at 100,000 he had a dealer fluid exchange at 45,000 and I did a pan drop and filter when I bought it.
I am only at 110,000 now so I am not much help but everything seems fine.
I have spent some time on the f150 forum and there is not a lot of discussion about trans problems, of course when you get over 200K any trans is probably a potential problem IMHO