My 5 D - Cell Maglite stopped working. I have new batteries in it and the bulb looks fine. I suspect that it's the switch. My maglite is 8 years old but its in very good condition. Will maglite replace or fix it? Any one have experience with Maglite's repair department? Should I send it back to them?
Replace the bulb to be doubly sure it isn't it. It may look fine but if you just replaced batteries it may have flashed the bulb. 5D - weigh up whether or not its worth your time sending it back to Maglite or just buy a new one.
You can actually visually determine that the bulb isn't broken? I guess what I'm getting at is I'm not able to see that very easily because the wound spring filament is so fine, and doesn't always fall out of place very far when it might have just a teeny space where it has burned apart.
Have you tried another bulb just for kicks?
 Oh, duh. That basically exactly what Onyx said. Sorry. I was in a rush and only read the 1st post.
the switch of maglites may cause the bulb to start flickering after time, but its not likely to fail. it most probably is your bulb. it could be your switch assembly though, if water has leaked in recently. happened to a 2D maglite of mine recently.
I've sent them Mag D-body flashlights that have literally seen 15+ years of extremely severe service - anodizing almost completely worn off, bodies dented and beaten into mere shadows of their former selves, etc. Mag hasn't replaced any of these, but has repaired every one.
I'd expect your light gets repaired rather than replaced.