Xbox 360's (Red Ring Of Death) and PS3's have their common faults, so yes I am predicting a certain degree of failure and if the fault is not covered by manufacturers warranties then you have to pay full price for the repairs, and we all know that going to Sony or Microsoft directly is the most expensive option, but, not the only option. That is where private individuals come into the mix.
Not all people will take out extended warranties either due to the fact there isn't alot of money flying around so buying a console is a big outlay and an absolute luxury. I among lots of other people will usually turn down the extended warranties anyway due to the bad value for money most of them provide, oh and huge amount of small print enabling them to crawl out of most repair jobs anyway.
Just take a look on Google and search for Xbox repairs or PS3 repairs and you'll see there's a massive market for repairers. When i ran my shop i used to run a service for a third party to repair consoles for my customers it was quite popular, so there is a good market for this type of thing, but i get what you mean as most major probs in the initial year SHOULD be fixed under warranty therefore it could be a year before i start seeing any significant traffic in the worst case scenario, but you'll always get little jonny dropping the thing or getting things jammed in the disc area etc so there should be some call for the service. (hopefully!)