I've been using and installing Outback inverters for 14 years. Most have never needed repair. The nice thing about the FX series is that you can repair them. They basically consist of 3 circuit boards and the big heavy transformer.
I've got 8 used ones in my shop right now that I traded in on a new Outback Radian. I went thru the old FX models, replaced the bad parts, and have them listed for sale now. Hopefully I'll make some money on the endeavor.
My entire house (except the heat pump, dryer, water heater) is backed-up by 2 VFX3648 inverters. They are 13 years old and never given a single problem.