The operation and maintenance manuals provided by your system installer should contain a schedule for regular maintenance, such as visual inspections and cleaning.
Clean solar panels can convert more light into electricity, so a panel clean might be worthwhile if they get too dirty, for example after a dust storm or bird droppings.
Inverters can also get dirty, for instance in a dusty environment inverters can lose some cooling capacity, leading potentially to power derating and premature failure.