The problem is the door structure rather than the hinges or carrier. Late
doors are supposed to be stronger, but cracking of the frame is quite
common at least on pre-TD5 doors, especially with oversize tyres and
corrugated roads. I had cracking on mine with standard tyres - but solved
the problem by backing into a tree, necessitating a new door. I rivetted
extra gussets in the frame of the new door and have had no problems with it
over eight years and 200,000km.
JD

With a standard 750R16 on my truck's rear door, the hinges started to
go, however it had done about 80,000 miles at the time.  The door
looked OK and the hinges are cheap, so if I hadn't converted to a
soft-top and removed the rear door, I'd probably have just got new
hinges rather than a wheel carrier.  Some people have seen door skins
stretch and/or door internal frames distort apparently, I suspect
regular off-roading (lots of jolts) wouldn't help.

I don't know if you can still get it but Land Rover used to sell a genuine
parts door strengthening kit for 90/110 rear doors. I don't remember the
part number or how much they were but I will have a look tomorrow if you are
interested, or ping Richard, maybe he can help.

Martin

Think it also depends on what your doingwith the Landy.  If it never
gets off the black stuff it'll probably be OK for ever and a day on
the original carrier.  Bouncing over stuff offroad will induce far
greater stresses and damage the door / hinge bushes over time.

Speak to Richard for a Mantec... Great bit of kit, last forever and
take ALL the weight off the door.

Jon