'Warranty' on Sony repairs is indeed a paltry 90 days.
Last November (2013) my A900 suffered a serious mechanical failure when the mirror separated from the support frame.
I was pleased when this was repaired under their fixed price scheme (I had bought the camera 2ns hand), but in May this year (2014) the mirror again detached - just as I was taking a shot to set custom white balance for my Father-in-Laws 70th birthday dinner - so no shots of the event
Contacted Sony, Pencoed repair centre said to contact customer Support, who insisted I pay again, and once the engineer had inspected the camera they would consider refunding it. Engineer confirmed it was the same problem, and that this time they would replace the entire mirror box assembly. Clearly the re-attach repair they had done previously had failed - Customer services, however, then simply said it was outside the 90 days, so would I was liable for the cost of repair!
I've just got my A900 back (a week ago), as they had trouble getting the parts...
IF it's properly fixed this time then it's not an excessive overall charge for such a replacement, but I'd have much rather they fixed it properly the first time.