Problem with clutch on cabstar

Been trying to find information on any problems with clutches on cabstars, i have 2, both on contract hire
2007 '07' reg, 34.11 SWB
2007 '07' reg 35.13 MWB
The first (34.11) suffered minor clutch problems from about 3months and had to be replaced under warrantee at 12months. The service garage told us that these were known to have a problem.
The second cabstar i have just had to have the clutch replaced, this also had minor problem (a small burning smell after reversing for some distance - although since we rarely reverse for more than a few metres this wasnt picked up very early on)), this seemed to get a little worse just after 12months but still only a niggle.
After its 18000 mile service it appeared to get marginally worse after sitting idle for 4 days over christmas break and the delivery driver had to reverse a long way down an alleyway giving a very pungent burnt smell from right behind the cab, i booked the cab in for the clutch to be inspected at approx 18months - 18500 miles.
The garage had no spare cabs for courtesy and with their ramp out of order we used the van lightly for a further 300miles and the clutch at this point was totally shot (really slipping).
Funnily enough once the garage inspected the clutch they said it was worn out, nissan refused warantee replacement and also goodwill replacement.
Should i expect a clutch to last for more than 18500 miles, most of these miles made up of short deliveries.
I just wanted to see if i could dig up a few documents of other people having similar problems before i contact nissan directly as i don't feel i have got reasonable use from the clutch
Cheers, David
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