Ok, so if solar panels are supposed to last 25 to 30 years, how many years can you expect your solar inverter to last?
A very good question, with no clear-cut answer, I'm afraid.
After installing and servicing inverters for over 14 years, I can suggest some typical patterns of failure.
One: Sub-standard components or deficient programming. Either of these can result in accelerated wear/aging of one or more components, resulting in a failure pattern with consistent, recognisable symptoms (eg consistent error message). Typically this can be the mains connection relay which is used to make the connection and disconnection to your premises electrical system. It has a limited number of operation cycles, and faulty control or sub-standard capability means it will fail prematurely. Even 'premium brands' are not exempt from this sort of behaviour!
Two: Changing or extreme mains/grid conditions result in accelerated wear. Typically, we see inverter models that have been in service for a number of years, now start failing. It includes inverters installed very recently, as well those installed a few years previously. Most of these we can only guess that these have succumbed to some sort of mains electrical disturbance, eg surges, spikes, increased 'street voltage' etc. Some we can put down to things like increased wear of the relay because the higher mains voltage now causes the relay to switch off and on again more frequently during the day.
Three: Hitting the limits of the technolgy lifetime. Manufacturers would ideally like to install electrical components that last forever, but instead settle with the best lifetime/economy ratio for that particular part. Eg, a transformer may last for a good many decades, but high-power capacitors are typically expected to last for only around 8 to 10 years. However, conservatively rated capacitors may well last longer. There are a myriad of other tricky little components that the design engineer must contend with in the process of design of the inverter.