2 Years Without Changing Oil?

I went several years before changing my genset oil because I only put 10 or 12 hrs a year on it. The dipstick was always clean and the level was good. When I did change it there was a lot of white creamy sludge in the bottom that did not show up on the dip stick. So condensation is a real problem especially over the winter, and even though I ran the genset before I drained the oil it did not burn off all that sludge. I don't know what an oil analyses would cost but I am sure it is more than my oil change and filter. I am sure there are a lot of variables as to were you live how long the engine sits between use etc, but I think a yearly oil change or every 12,000 miles is good advice.