Synthetic oil worth it? 18k hour yamaha generator says no.

I use synthetic in my lawn tractor, snow blower, tiller, and 5500w generator. I change it every couple of years and have never had an engine failure.
I recently got the Smarter Tools 2000w inverter generator for camping and it has the Yamaha M80 engine. At $600, I am sure it is made in China. Once I get through the break in period, it will get synthetic as well.