Thanks chaps, some interesting info.
I actually thought I'd read on here about the apu starter motor brushes in a previous thread/search - rookie error, my apologies.
To clear up some rationale:
I'm not settling a bet, nor casting any aspersions on any maintenance regimes
However I've been lurking for years on this forum, just reading out of personal interest, never had anything to contribute as I'm not in this industry. I only chose to sign up and post because there are some clued up guys here who would (might) respond with specific knowledge/experience.
That said, it is indeed with regards to a flight delay caused by starter failure, I am asking on behalf of a colleague (yes really! lol), who has already been told 'no - extra ordinary circumstances etc etc'. She isn't going to do anything else, but from a personal interest perspective I wanted to know what could fail (and why), how long it might take to fix etc.
Is it like a car starter, unbolt/replace etc (obviously it's clearly not).
One of the final points which was sent in her 'no' response was that the replacement starter was sourced from the airlines 'home base'... so I wondered if this was necessary - or would it be like the equivalent of 'eurocarparts' where a replacement unit could be found from another major airport/base?