i had a w reg which was great, replaced three wheel bearings and clutch, i put the clutch down to what i was doing with it , lots of towing and to be honest it didnt need a clutch, the release bearing was noisy so i changed it. mine was a billy basic model , no engine or gearbox issues.
my mate still has the disco and its now had the fourth wheel bearing and another replaced a second time and recently had its first chassis patch, funnily enough in a strange place at the front.
like most motors its down to how its been treated and serviced, bet the diff is on its factory oil.
i always changed the fluids on time with quality stuff and both oil filters at the same time. having had a 200,300,td5 and disco three i would say the td5 was my favorite and to be honest i regret selling it, maybe cause the disco three was such a bucket of poo.