Something else is wrong if that is as long as it is lasting. Park on grass?

Fuel issue? Head gasket?

Frankly even cheap aftermarket should last longer, and with ULSD fuel, the sulfur corrosion problem has gone away.

Id reconsider everything else if that is the life you're getting.

__________________
Current Diesels:
1981 240D (73K)
1982 300CD (169k)
1985 190D (169k)
1991 350SD (116k)
1991 350SD (206k)
1991 300D (228k)
2008 ML320 CDI (199k)
1996 Dodge Ram CTD (442k)
1996 Dodge Ram CTD (267k)

Past Diesels:
1983 300D (228K), 1985 300D (233K), 1993 300D 2.5T (338k), 1993 300SD (291k)