I had that trouble - not excessive, but enough to warrant doing something. ISTR there was a very thick spacer washer between flange and nut, I did get another (yes, from Maidstone Kia!) but it didn't make too much difference.
What is your propshaft like? The sliding splines get very bad so you can lift the prop up a fair bit, and it is that constant radial movement I think which trashes the U/Js and then starts on the transfer box flange.
I put a N.O.S. prop on last year when I changed the flange washer, and within a year it is getting well worn again! Next time I'll get a quality propshaft made up, but space is very tight beside the 5 speed box for a bigger diameter shaft :cool2:.