Old Thread, i'm in power generation field service, I see this on a daily basis. Nothing wrong with taking fluid samples and inspecting the generator and transfer switch(s) for proper operation.
CAT put out the option to offer 3 year oil change cycle on CAT diesels C9 and larger in Standby Power application. Can do this by taking quarterly samples and annual filter replacement, still maintain CAT warranty or ESC.
I can tell you a very large telecom company mandates oil changes are to be performed every 3 years or per sample analysis on standby generators.
Still you have issues with engines sitting, injector cups leaking coolant, oil cooler leaking, head gasket or fuel dilution. Just changing the engine oil won't correct these issues and only mask them over for a short period.
Hope this helps.