If starting is that difficult, I'd suggest that something else is wrong - possibly poor engine earth.
I've had my JTD for almost 9 years & 137K on the clock - I dont purposely wait for the glowplug light to go out, I normally insert the key and crank the engine immediately. Even in this current cold weather the engine catches immediately.
The only time I had problems was when the original battery died, probably tempting fate, but that was 5 years ago!! Perhaps my 85 mile daily roundtrip to work does have some benefit and prolongs battery life?