Volkswagen Repair: 2003 TDI, weather environments, engine indication

Question
I have a TDI 2003  I had to replace the glow plugs at 32ooo.  It was covered under warrenty because the wiring harness was bad.  Now I need to replace them again after 25ooo miles.  They will not replace because it is not under warranty.  I know that glow plugs are a consumable but shouldn't they last longer than 25-35ooo miles.  The car is made for the plugs to come on when you open the door.  Should a push this or just have them fixed??

Answer
Glow plugs are especially required in cold weather environments.  If you don't have cold/hard starting problems, I guess you can do without them, however you may get a constant "check engine" indication.  Also there are several glow plugs with different purposes, so I don't know if this next "glow plug" problem is actually a different component.  Further, given the environment and stress these components take, in my opinion 25,000 miles doesn't seem like an unreasonable life expectancy.